Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0003777 microtubule motor activity	IBA GO_REF:0000033	ACCEPT	Summary: Phylogenetic (IBA) support for microtubule motor activity, redundant with the experimental IDA below (PMID:17000880). Correct core molecular function of the kinesin motor domain. The more specific term is plus-end-directed microtubule motor activity (GO:0008574), captured in core_functions. Supporting Evidence: PMID:17000880 indicating that Mg-ATP is the preferred substrate for kinesin-2 motors
GO:0005737 cytoplasm	IBA GO_REF:0000033	KEEP AS NON CORE	Summary: Broad cytoplasmic localization consistent with UniProt (Cytoplasm, cytoskeleton by similarity), but uninformative relative to the specific ciliary localization. Keep as non-core context.
GO:0008017 microtubule binding	IBA GO_REF:0000033	ACCEPT	Summary: Microtubule binding is intrinsic to the kinesin motor domain and required for the motor to engage its track. Correct and consistent with plus-end-directed motor activity; retained as a supporting molecular function.
GO:0060271 cilium assembly	IBA GO_REF:0000033	ACCEPT	Summary: Kinesin-II (with klp-20 as a motor subunit) and osm-3 move IFT particles that redundantly build the sensory cilium foundation, so involvement in cilium assembly is well supported. Accept as a core biological process. Supporting Evidence: PMID:17000880 either motor but not both being dispensable for this function
GO:0005871 kinesin complex	IBA GO_REF:0000033	KEEP AS NON CORE	Summary: Correct but general parent of the specific complex membership. klp-20 is a subunit of the (axonemal heterotrimeric) kinesin-II complex; the specific terms GO:0016939/GO:0030993 are preferred. Keep as non-core.
GO:0005874 microtubule	IBA GO_REF:0000033	KEEP AS NON CORE	Summary: The microtubule is the motor's track rather than a distinct cellular location of the protein. Consistent with function but non-core; the informative location is the cilium.
GO:0016887 ATP hydrolysis activity	IBA GO_REF:0000033	ACCEPT	Summary: ATP hydrolysis powers the kinesin motor; the motor domain of klp-20 contains the P-loop (Walker A) ATPase site, and purified kinesin-II shows Mg-ATP-dependent motility with Michaelis-Menten kinetics (PMID:17000880). Accept as part of the core motor mechanism. Supporting Evidence: PMID:17000880 kinesin-II–driven motility conformed to Michaelis-Menten kinetics
GO:0008089 anterograde axonal transport	IBA GO_REF:0000033	MARK AS OVER ANNOTATED	Summary: This term is a phylogenetic transfer from kinesin-II orthologs (KIF3) that act in neuronal axonal transport. In C. elegans the documented role of klp-20/kinesin-II is anterograde intraflagellar (ciliary) transport, not classical axonal cargo transport; there is no experimental evidence for a klp-20 axonal-transport role in worm. Treated as an over-propagated electronic inference; the accurate specific term is intraciliary anterograde transport (GO:0035720). Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: CONTEXT OR TISSUE MISMATCH GRANULARITY MISMATCH Sources checked: FB:FBgn0004380 · Klp64D (Drosophila kinesin-II KIF3A ortholog) SUPPORTS SOURCE BUT NOT TARGET Kinesin-II orthologs act in neuronal anterograde axonal transport, but the documented C. elegans klp-20 role is anterograde intraciliary transport, not axonal cargo transport; the axon-specific term does not transfer. PANTHER:PTN000650181 · kinesin-2 anterograde-transport node SUPPORTS SOURCE BUT NOT TARGET Node-level anterograde-transport inference; the ciliary (GO:0035720) rather than axonal (GO:0008089) child is the correct scoping for klp-20.
GO:0003777 microtubule motor activity	IEA GO_REF:0000120	ACCEPT	Summary: Electronic (InterPro/ARBA) support for microtubule motor activity, redundant with the experimental IDA (PMID:17000880) and the IBA above. Correct core molecular function.
GO:0005524 ATP binding	IEA GO_REF:0000002	ACCEPT	Summary: ATP binding via the conserved P-loop/Walker A motif of the kinesin motor domain (UniProt BINDING 91..98). Correct molecular-mechanism support for the ATP-driven motor; retained as supporting.
GO:0005856 cytoskeleton	IEA GO_REF:0000120	KEEP AS NON CORE	Summary: General cytoskeletal localization from an electronic subcellular-location rule. Consistent with a microtubule motor but non-specific; the informative location is the cilium.
GO:0005929 cilium	IEA GO_REF:0000120	ACCEPT	Summary: Ciliary localization is well established: klp-20/kinesin-II functions in sensory cilia and UniProt records SUBCELLULAR LOCATION cilium (localizing to the base and transition zone; PMID:28479320). Accept as a core cellular location.
GO:0007018 microtubule-based movement	IEA GO_REF:0000120	ACCEPT	Summary: Electronic support for microtubule-based movement, redundant with the experimental IDA (PMID:17000880). Correct but general; the specific process is intraciliary anterograde transport (GO:0035720). Accept.
GO:0008017 microtubule binding	IEA GO_REF:0000002	ACCEPT	Summary: Electronic (InterPro) support for microtubule binding, redundant with the IBA above and intrinsic to the motor domain. Accept as supporting molecular function.
GO:0032991 protein-containing complex	IEA GO_REF:0000117	MARK AS OVER ANNOTATED	Summary: Root-level complex membership from an ARBA rule. True (klp-20 is part of kinesin-II) but uninformative; the specific complex terms GO:0016939 and GO:0030993 supersede it. Over-annotated at this level of generality.
GO:1904115 axon cytoplasm	IEA GO_REF:0000108	MARK AS OVER ANNOTATED	Summary: Inferred logically (GO_REF:0000108) from the anterograde axonal transport annotation (GO:0008089), which is itself an over-propagated phylogenetic transfer. klp-20 acts in sensory cilia in C. elegans, not documented axoplasm; this location is a downstream consequence of the over-annotated axonal-transport term.
GO:0007018 microtubule-based movement	NAS PMID:20498083 Regulation of a heterodimeric kinesin-2 through an unprocess...	ACCEPT	Summary: ComplexPortal NAS annotation for microtubule-based movement, supported by the biophysical characterization of the KLP-11/KLP-20 heterodimer motor. Correct but general relative to intraciliary anterograde transport; accept. Supporting Evidence: PMID:20498083 One motor domain is unprocessive as a homodimer
GO:0016939 kinesin II complex	NAS PMID:20498083 Regulation of a heterodimeric kinesin-2 through an unprocess...	ACCEPT	Summary: klp-20 is a subunit of the kinesin II complex (the klp-11/klp-20/kap-1 heterotrimer). Directly supported: heterodimerization of klp-20 with klp-11 is required to bind kap-1 (PMID:20498083), and the purified heterotrimer was characterized in PMID:17000880. Accept as core complex membership; the axonemal term GO:0030993 is the most specific. Supporting Evidence: PMID:20498083 heterodimerization is necessary to bind KAP1, the in vivo link between motor and
GO:0035720 intraciliary anterograde transport	NAS PMID:20498083 Regulation of a heterodimeric kinesin-2 through an unprocess...	ACCEPT	Summary: Anterograde IFT is the core biological process of kinesin-II. As a kinesin-II motor subunit, klp-20 drives base-to-tip transport of IFT particles along sensory cilia together with osm-3. Accept as a core process. Supporting Evidence: PMID:17000880 two anterograde IFT motors called kinesin-II and OSM-3
GO:0003777 microtubule motor activity	IDA PMID:17000880 Mechanism of transport of IFT particles in C. elegans cilia ...	ACCEPT	Summary: Direct experimental (IDA) annotation from characterization of purified kinesin-II, which contains klp-20 as one of its two motor subunits and moves microtubules in an ATP-dependent manner. This is the strongest evidence for the core molecular function. The most specific term is plus-end-directed microtubule motor activity (GO:0008574), used in core_functions. Supporting Evidence: PMID:17000880 the KLP-11, KAP-1, and KLP-20 subunits elute as a monodisperse heterotrimeric complex
GO:0007018 microtubule-based movement	IDA PMID:17000880 Mechanism of transport of IFT particles in C. elegans cilia ...	ACCEPT	Summary: Direct experimental annotation for microtubule-based movement from the kinesin-II gliding assays. Correct; general relative to intraciliary anterograde transport but experimentally solid. Accept. Supporting Evidence: PMID:17000880 indicating that Mg-ATP is the preferred substrate for kinesin-2 motors
GO:0030993 axonemal heterotrimeric kinesin-II complex	IPI PMID:17000880 Mechanism of transport of IFT particles in C. elegans cilia ...	ACCEPT	Summary: Direct physical-interaction (IPI) evidence that klp-20 is a subunit of the axonemal heterotrimeric kinesin-II complex, purified as a monodisperse heterotrimer of KLP-11/KLP-20/KAP-1 (with WormBase klp-11 and kap-1 as the with/from partners). This is the most specific and best-supported complex-membership term and the core cellular-component annotation. Supporting Evidence: PMID:17000880 consisting of 1 mol each of its subunits KLP-11, KLP-20, and KAP-1 with a native molecular mass of 287 kD
GO:0008574 plus-end-directed microtubule motor activity	IDA PMID:17000880 Mechanism of transport of IFT particles in C. elegans cilia ...	NEW	Summary: Proposed refinement of the experimental microtubule motor activity annotation (GO:0003777, IDA, PMID:17000880) to the more specific plus-end-directed microtubule motor activity. Kinesins are plus-end-directed motors and kinesin-II (with klp-20) drives anterograde (base-to-tip, plus-end-directed) IFT; the purified motor moves microtubules in gliding assays. This is the primary core molecular function. Supporting Evidence: PMID:17000880 kinesin-II alone moved MTs at a maximal rate of 0.3

Core Functions

As one of the two motor subunits of heterotrimeric kinesin-II (klp-11/klp-20/kap-1), klp-20 contributes to the ATP-driven, microtubule plus-end-directed motor activity of the complex. klp-20 heterodimerizes with klp-11 through its C-terminal coiled-coil stalk; this heterodimer is processive and binds the accessory subunit kap-1, which couples the motor to IFT cargo. The motor moves along the doublet microtubules of the sensory-cilium middle segment.

Molecular Function:

plus-end-directed microtubule motor activity

Directly Involved In:

intraciliary anterograde transport cilium assembly

Cellular Locations:

cilium

In Complex:

axonemal heterotrimeric kinesin-II complex

Supporting Evidence:

PMID:17000880
the KLP-11, KAP-1, and KLP-20 subunits elute as a monodisperse heterotrimeric complex
PMID:20498083
heterodimerization is necessary to bind KAP1, the in vivo link between motor and

The kinesin motor domain of klp-20 hydrolyzes ATP to power microtubule-based movement. Purified kinesin-II (containing klp-20) uses Mg-ATP as its preferred substrate with Michaelis-Menten kinetics, and klp-20 carries the conserved P-loop (Walker A) ATP-binding motif.

Molecular Function:

ATP hydrolysis activity

In Complex:

axonemal heterotrimeric kinesin-II complex

Supporting Evidence:

PMID:17000880
indicating that Mg-ATP is the preferred substrate for kinesin-2 motors

References

GO_REF:0000002

Gene Ontology annotation through association of InterPro records with GO terms

GO_REF:0000033

Annotation inferences using phylogenetic trees

GO_REF:0000108

Automatic assignment of GO terms using logical inference, based on on inter-ontology links

GO_REF:0000117

Electronic Gene Ontology annotations created by ARBA machine learning models

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

PMID:17000880

Mechanism of transport of IFT particles in C. elegans cilia by the concerted action of kinesin-II and OSM-3 motors.

Purified recombinant kinesin-II behaves as a monodisperse heterotrimer of the KLP-11, KLP-20 and KAP-1 subunits (native mass ~287 kD, 1:1:1 stoichiometry), establishing klp-20 as a subunit of the heterotrimeric kinesin-II complex.

"the KLP-11, KAP-1, and KLP-20 subunits elute as a monodisperse heterotrimeric complex"
Kinesin-II (containing klp-20) is an ATP-driven microtubule motor; in gliding assays it moves microtubules and uses Mg-ATP by Michaelis-Menten kinetics.

"indicating that Mg-ATP is the preferred substrate for kinesin-2 motors"
Kinesin-II and OSM-3 are the two anterograde IFT motors that redundantly move IFT particles to build the sensory cilium foundation.

"two anterograde IFT motors called kinesin-II and OSM-3"

PMID:20498083

Regulation of a heterodimeric kinesin-2 through an unprocessive motor domain that is turned processive by its partner.

The KLP-11/KLP-20 heterodimer pairs an unprocessive with a processive motor domain; heterodimerization generates processivity.

"One motor domain is unprocessive as a homodimer"
Heterodimerization of klp-20 with klp-11 is required to bind KAP-1, the in vivo link between the motor and its cargo.

"heterodimerization is necessary to bind KAP1, the in vivo link between motor and"

Suggested Experiments

Experiment: Single-molecule motility (TIRF) comparison of purified klp-20 homodimer, klp-11 homodimer, and klp-11/klp-20 heterodimer with subunit-specific fluorophores, to assign processivity and duty ratio to each subunit and test the asymmetric-autoregulation model.

Hypothesis: klp-20 and klp-11 have different intrinsic processivities, and one specific subunit is the unprocessive, autoregulatory head.

Experiment: In vivo IFT imaging (kymography of fluorescently tagged IFT components) in klp-20 loss-of-function versus osm-3 loss-of-function animals to define the cargoes and axonemal segments whose transport specifically depends on the klp-20-containing kinesin-II motor.

Hypothesis: The klp-20-containing kinesin-II motor is specifically required for anterograde transport of a defined subset of IFT cargoes along the middle (doublet) segment.

Knowledge Gaps

What is not known — curated, literature-grounded statements of the open unknowns (the inverse of core functions).

Gap: Within the klp-11/klp-20 heterodimer it is not resolved which subunit is the "unprocessive" motor domain and which is the processive one — i.e. whether klp-20 itself is the processive or the autoinhibited/unprocessive head, and the residue-level basis of its individual duty ratio.

OPEN BIOLOGY RESIDUAL_SUBGAP

What is known: It is established that heterodimerization of the two distinct C. elegans kinesin-2 motor domains converts an otherwise unprocessive homodimer into a processive heterodimer, that the unprocessive subunit mediates an asymmetric autoregulation of motor activity, and that the heterodimer must form to bind kap-1 (the cargo link). UniProt annotates two klp-20 residues (444, 445) as possibly required for autoinhibition within the heterodimer.

Significance: Kinesin-2 heterodimerization is the paradigm for how obligate motor heterodimers tune processivity and autoregulation; assigning the processive vs unprocessive role to klp-20 vs klp-11 defines the mechanistic division of labor of the anterograde IFT motor.

What would resolve it: Single-molecule processivity assays on defined homodimeric vs heterodimeric constructs of the klp-20 and klp-11 motor domains, with subunit-specific labeling and head-tracking to assign duty ratio to each subunit.

Provenance (the field's own admissions):

"One motor domain is unprocessive as a homodimer" — PMID:20498083
"asymmetric autoregulation of the motor" — PMID:20498083

Gap: The direct, klp-20-motor-selected ciliary cargo repertoire is not enumerated: what cargoes the klp-20-containing kinesin-II specifically delivers is inferred through the IFT-A/IFT-B particle rather than measured for the motor itself.

OPEN BIOLOGYCURATION BP_DARK

What is known: Kinesin-II (with klp-20 as a motor subunit) and osm-3 are the two anterograde IFT motors that move IFT particles to build the sensory cilium foundation; kap-1 provides the in vivo link between the motor and cargo.

Significance: Defining the motor-specific cargo would clarify how the two anterograde IFT motors (kinesin-II vs osm-3) divide cargo responsibilities along the ciliary axoneme, which is central to understanding ciliogenesis and ciliopathy.

What would resolve it: Proximity labeling or cargo-trapping proteomics on the klp-20/kap-1 motor in cilia, combined with klp-20 loss-of-function IFT imaging to identify cargoes whose ciliary delivery specifically requires the klp-20-containing motor.

Provenance (the field's own admissions):

"heterodimerization is necessary to bind KAP1, the in vivo link between motor and" — PMID:20498083

Deep Research

Falcon

(klp-20-deep-research-falcon.md)

Comprehensive Research Report: *klp-20* (Kinesin-Like Protein 20) in *Caenorhabditis elegans* Falcon Edison Scientific Literature 15 citations 1 artifacts 2026-07-04T20:25:34.223036

Edison artifact artifact-00 (text/markdown)

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Comprehensive Research Report: klp-20 (Kinesin-Like Protein 20) in Caenorhabditis elegans

1. Gene and Protein Identity

The gene klp-20 (ORF name Y50D7A.6; UniProt accession Q965T6) encodes a kinesin-like protein in Caenorhabditis elegans. KLP-20 belongs to the TRAFAC class myosin-kinesin ATPase superfamily and contains a canonical kinesin motor domain (InterPro: IPR001752), a kinesin-like family domain (IPR027640), a P-loop NTPase domain (IPR027417), and a kinesin motor domain conserved site (IPR019821). These domains are diagnostic of a microtubule-dependent motor protein that couples ATP hydrolysis to directional movement along microtubule tracks.

The summary of KLP-20's key properties is provided below:

Property	Value
Gene name	klp-20 (maguire2015myristoylatedcil7is pages 13-17)
ORF name	Y50D7A.6
UniProt accession	Q965T6
Protein family	Kinesin-2 / heterotrimeric kinesin-II; TRAFAC-class myosin-kinesin ATPase superfamily (maguire2015myristoylatedcil7is pages 13-17, nakayama2018ciliaryproteintrafficking pages 4-5)
Complex partners	KLP-11 and KAP-1 form the heterotrimeric kinesin-II complex with KLP-20 (maguire2015myristoylatedcil7is pages 13-17, nakayama2018ciliaryproteintrafficking pages 4-5)
Mammalian ortholog / counterpart	Functional counterpart within the mammalian heterotrimeric kinesin-II complex: KIF3B (with KIF3A and KAP3/KIFAP3) (nakayama2018ciliaryproteintrafficking pages 4-5, verhey2011kinesinmotorsand pages 2-4)
Molecular function	ATP-dependent microtubule motor that drives anterograde intraflagellar transport (IFT) of IFT complexes/cargo during ciliogenesis and ciliary maintenance (maguire2015myristoylatedcil7is pages 13-17, maguire2015myristoylatedcil7is pages 7-13, verhey2011kinesinmotorsand pages 2-4)
Subcellular localization	Cilia of ciliated sensory neurons, including amphids, phasmids, IL2 neurons, and male-specific sensory neurons (maguire2015myristoylatedcil7is pages 13-17, maguire2015myristoylatedcil7is pages 7-13)
Motor velocity alone	~0.5 μm/s for kinesin-II anterograde movement in amphid channel cilia / transition zone loading phase (maguire2015myristoylatedcil7is pages 13-17, prevo2017intraflagellartransportmechanisms pages 33-35, prevo2017intraflagellartransportmechanisms pages 12-14)
Motor velocity with OSM-3	~0.7 μm/s when kinesin-II and OSM-3 co-transport IFT trains in the middle segment (maguire2015myristoylatedcil7is pages 13-17, prevo2017intraflagellartransportmechanisms pages 12-14)
Key biological process	Intraflagellar transport supporting cilia assembly, maintenance, and organization of middle/proximal ciliary segments (nakayama2018ciliaryproteintrafficking pages 4-5, li2024regulationofciliary pages 3-5)
Functional division of labor	Kinesin-II loads/navigates IFT trains through the transition zone and cooperates with OSM-3 in the middle segment; OSM-3 alone builds/transports in the distal segment (prevo2017intraflagellartransportmechanisms pages 33-35, maguire2015myristoylatedcil7is pages 13-17, prevo2017intraflagellartransportmechanisms pages 12-14)
Mutant phenotype	In single mutants of heterotrimeric kinesin-II genes including klp-20, amphid chemosensory cilia are maintained because OSM-3 compensates; thus klp-20 loss alone yields a relatively mild/partially redundant ciliary phenotype (verhey2011kinesinmotorsand pages 2-4)

Table: This table summarizes the core annotated and literature-supported properties of C. elegans KLP-20, including its kinesin-II complex membership, ciliary localization, transport role, velocities, and mutant behavior. It is useful as a compact reference for functional annotation.

2. Molecular Function and Enzymatic Activity

KLP-20 is one of the two motor subunits of the C. elegans heterotrimeric kinesin-II complex, a member of the kinesin-2 family (maguire2015myristoylatedcil7is pages 13-17, nakayama2018ciliaryproteintrafficking pages 4-5). The heterotrimeric kinesin-II complex consists of two distinct motor subunits, KLP-20 and KLP-11, plus the non-motor accessory subunit KAP-1 (maguire2015myristoylatedcil7is pages 13-17, maguire2015myristoylatedcil7is pages 7-13). This complex is the functional ortholog of the mammalian heterotrimeric kinesin-II comprising KIF3A, KIF3B, and KAP3/KIFAP3, with KLP-20 serving as the functional counterpart of KIF3B (nakayama2018ciliaryproteintrafficking pages 4-5, verhey2011kinesinmotorsand pages 2-4).

As a kinesin motor protein, KLP-20 functions as an ATP-dependent microtubule-based motor. The enzymatic reaction catalyzed is the hydrolysis of ATP to ADP and inorganic phosphate (Pi), and this chemical energy is coupled to plus-end-directed translocation along microtubule tracks. The substrate is ATP (with Mg²⁺ as a cofactor), and the protein generates mechanical force through conformational changes in the motor domain upon nucleotide binding and hydrolysis. The kinesin motor domain contains a P-loop NTPase fold characteristic of this superfamily.

3. Biological Function: Intraflagellar Transport (IFT)

The primary biological function of KLP-20, as part of the heterotrimeric kinesin-II complex, is to drive anterograde intraflagellar transport (IFT) in the cilia of sensory neurons (maguire2015myristoylatedcil7is pages 13-17, maguire2015myristoylatedcil7is pages 7-13, nakayama2018ciliaryproteintrafficking pages 4-5). IFT is an essential, highly conserved mechanism for the assembly, maintenance, and function of cilia. During IFT, kinesin-II assembles with IFT particle complexes (IFT-A and IFT-B) and associated cargoes—including axoneme precursors, ciliary membrane proteins, signaling molecules, and retrograde motors—and drives their anterograde (base-to-tip) transport along axonemal microtubules (maguire2015myristoylatedcil7is pages 13-17, verhey2011kinesinmotorsand pages 2-4).

3.1 Cooperation with OSM-3

A distinguishing feature of IFT in C. elegans sensory cilia is the cooperative action of two kinesin-2 motors: the heterotrimeric kinesin-II (containing KLP-20/KLP-11/KAP-1) and the homodimeric kinesin-2 motor OSM-3 (the C. elegans ortholog of mammalian KIF17) (maguire2015myristoylatedcil7is pages 13-17, li2024regulationofciliary pages 3-5). These two motors have distinct velocities and roles:

Kinesin-II alone moves at approximately 0.5 μm/s in the anterograde direction and functions as a "loader" and "navigator," loading IFT trains at the ciliary base and transporting them through the transition zone (maguire2015myristoylatedcil7is pages 13-17, prevo2017intraflagellartransportmechanisms pages 12-14).
OSM-3 alone moves at approximately 1.3–1.5 μm/s and acts as the long-range transporter in the distal ciliary segment (prevo2017intraflagellartransportmechanisms pages 33-35, prevo2017intraflagellartransportmechanisms pages 12-14).
When both motors are present on the same IFT train in the middle (proximal) segment, they produce an intermediate velocity of approximately 0.7 μm/s (maguire2015myristoylatedcil7is pages 13-17, prevo2017intraflagellartransportmechanisms pages 12-14).

This cooperation involves a coordinated motor handover mechanism: as IFT trains move distally along the middle segment, kinesin-II gradually undocks from the trains while OSM-3 motors simultaneously dock, causing progressive acceleration. In the distal segment, OSM-3 alone occupies the trains, reaching terminal velocity. During retrograde transport, IFT dynein returns the trains to the base while recycling OSM-3, and kinesin-II gradually re-docks along the proximal segment (prevo2017intraflagellartransportmechanisms pages 33-35).

3.2 Role in Ciliary Segment Assembly

The C. elegans amphid channel cilia exhibit a characteristic bipartite structure with a middle segment containing nine microtubule doublets and a distal segment containing nine microtubule singlets. Kinesin-II and OSM-3 work together redundantly to build the middle segment, while OSM-3 alone is responsible for constructing the distal segment (nakayama2018ciliaryproteintrafficking pages 4-5, maguire2015myristoylatedcil7is pages 13-17, li2024regulationofciliary pages 3-5, prevo2017intraflagellartransportmechanisms pages 15-17). The handover zone between kinesin-II and OSM-3 defines the boundary between proximal and distal ciliary compartments, and this boundary is regulated by kinases such as CDKL-1 (park2021cdklkinaseregulates pages 1-3, park2021cdklkinaseregulates pages 12-13).

4. Subcellular Localization

KLP-20, as part of the heterotrimeric kinesin-II complex, is expressed and functions within the cilia of all ciliated sensory neurons in C. elegans (maguire2015myristoylatedcil7is pages 13-17, maguire2015myristoylatedcil7is pages 7-13). In adult hermaphrodites, 60 of 302 neurons possess ciliated dendritic endings, including the amphid neurons (primary chemosensory organs in the head), phasmid neurons (chemosensory organs in the tail), inner labial neurons (IL1, IL2), and various other sensory neurons. Male C. elegans possess an additional ~50 ciliated sensory neurons involved in mating behaviors (maguire2015myristoylatedcil7is pages 7-13). Specifically, KLP-20 localizes to the ciliary compartment where it carries out anterograde IFT along the axoneme, with highest concentration in the transition zone and middle (proximal) segment of cilia (prevo2017intraflagellartransportmechanisms pages 33-35, prevo2017intraflagellartransportmechanisms pages 12-14).

5. Mutant Phenotype and Genetic Redundancy

A notable aspect of KLP-20 function in C. elegans is its partial redundancy with OSM-3. In single mutants of any of the heterotrimeric kinesin-II genes (klp-11, klp-20, or kap-1), the non-motile cilia at the dendritic endings of amphid chemosensory neurons are maintained, because OSM-3 compensates for the loss of kinesin-II function (verhey2011kinesinmotorsand pages 2-4). This contrasts sharply with the situation in most other organisms, where loss of heterotrimeric kinesin-II leads to a complete absence of cilia. In mammals, for example, deletion of either Kif3a or Kif3b results in a "no cilia" phenotype (nakayama2018ciliaryproteintrafficking pages 4-5). The unique redundancy in C. elegans was established through studies showing that kinesin-II and OSM-3 work cooperatively and redundantly in the middle region of ASH/ASI channel and AWC wing cilia, whereas OSM-3 works alone to build the distal region (verhey2011kinesinmotorsand pages 2-4). However, this compensation is not universal across all cilia types in C. elegans; the roles of kinesin-2 and OSM-3 differ across different chemosensory neuron types within the amphid organ (verhey2011kinesinmotorsand pages 2-4).

6. Regulation by Tubulin Post-Translational Modifications

The activity of kinesin motors in C. elegans cilia, including kinesin-II, is regulated by the "tubulin code"—a system of tubulin post-translational modifications (PTMs) including glutamylation. The glutamylase TTLL-11 and deglutamylase CCPP-1 fine-tune tubulin glutamylation levels in cilia, which in turn regulates motor protein activity and cargo transport (o’hagan2017glutamylationregulatestransport pages 4-5, o’hagan2017glutamylationregulatestransport pages 1-3). Interestingly, while CCPP-1-mediated regulation affects the velocities of OSM-3/KIF17 and KLP-6 (a kinesin-3 motor), it does not appear to directly affect the anterograde transport mediated by heterotrimeric kinesin-II (o’hagan2017glutamylationregulatestransport pages 4-5, o’hagan2017glutamylationregulatestransport pages 1-3). In vitro studies have shown that polyglutamylation of tubulin increases both the processivity and velocity of kinesin-2 motors (o’hagan2017glutamylationregulatestransport pages 7-8). The transport of the glutamylase TTLL-11 by ciliary kinesins creates a feedback mechanism whereby the motors transport the very enzyme that modifies the microtubule tracks on which they run (o’hagan2017glutamylationregulatestransport pages 9-10, o’hagan2017glutamylationregulatestransport pages 9-9).

7. Pathway Context and Broader Significance

KLP-20 functions within the intraflagellar transport pathway, which is central to ciliogenesis and ciliary homeostasis. The IFT pathway involves: (1) assembly of IFT trains (composed of IFT-A and IFT-B particle complexes) at the ciliary base; (2) anterograde transport by kinesin-2 motors (kinesin-II and OSM-3) delivering axonemal building blocks and signaling molecules to the ciliary tip; (3) cargo unloading and IFT train remodeling at the ciliary tip; and (4) retrograde transport by IFT dynein returning components to the base (prevo2017intraflagellartransportmechanisms pages 33-35, prevo2017intraflagellartransportmechanisms pages 15-17, verhey2011kinesinmotorsand pages 2-4). Heterotrimeric kinesin-II interacts with the IFT-B complex at the interface between the core and peripheral subcomplexes (nakayama2018ciliaryproteintrafficking pages 4-5).

The conservation of the heterotrimeric kinesin-II complex from nematodes to mammals underscores its fundamental importance in cilia biology. Mutations in ciliary genes, including those encoding IFT motors and their regulators, cause a growing class of pleiotropic human diseases known as ciliopathies. While KLP-20 itself is a C. elegans-specific gene name, its mammalian counterpart KIF3B is essential for ciliogenesis, and loss of KIF3B in mice results in a complete absence of cilia (nakayama2018ciliaryproteintrafficking pages 4-5).

8. Summary

KLP-20 is a kinesin-2 family motor protein that functions as one of the two motor subunits of the C. elegans heterotrimeric kinesin-II complex, together with KLP-11 and the accessory subunit KAP-1. Its primary molecular function is ATP-dependent, plus-end-directed translocation along ciliary microtubules, driving anterograde intraflagellar transport in all ciliated sensory neurons. KLP-20 cooperates with the homodimeric kinesin-2 motor OSM-3 to build the middle segments of sensory cilia, with a motor handover mechanism ensuring smooth cargo delivery along different ciliary compartments. The partial functional redundancy between kinesin-II and OSM-3 in C. elegans means that klp-20 single mutants maintain cilia structure, a feature distinct from most other organisms. KLP-20's activity is influenced by the tubulin code, including glutamylation of axonemal microtubules, and it operates within the broader IFT pathway that is essential for cilia assembly, maintenance, and sensory signaling.

References

(maguire2015myristoylatedcil7is pages 13-17): Julie Elizabeth Maguire. Myristoylated cil-7 is required for polycystin associated behaviors and extracellular vesicle biogenesis in c. elegans. ArXiv, Jan 2015. URL: https://doi.org/10.7282/t3cr5w7w, doi:10.7282/t3cr5w7w. This article has 0 citations.
(nakayama2018ciliaryproteintrafficking pages 4-5): Kazuhisa Nakayama and Yohei Katoh. Ciliary protein trafficking mediated by ift and bbsome complexes with the aid of kinesin-2 and dynein-2 motors. Journal of biochemistry, 163 3:155-164, Mar 2018. URL: https://doi.org/10.1093/jb/mvx087, doi:10.1093/jb/mvx087. This article has 160 citations and is from a peer-reviewed journal.
(verhey2011kinesinmotorsand pages 2-4): Kristen J. Verhey, John Dishinger, and Hooi Lynn Kee. Kinesin motors and primary cilia. Biochemical Society transactions, 39 5:1120-5, Oct 2011. URL: https://doi.org/10.1042/bst0391120, doi:10.1042/bst0391120. This article has 108 citations and is from a peer-reviewed journal.
(maguire2015myristoylatedcil7is pages 7-13): Julie Elizabeth Maguire. Myristoylated cil-7 is required for polycystin associated behaviors and extracellular vesicle biogenesis in c. elegans. ArXiv, Jan 2015. URL: https://doi.org/10.7282/t3cr5w7w, doi:10.7282/t3cr5w7w. This article has 0 citations.
(prevo2017intraflagellartransportmechanisms pages 33-35): Bram Prevo, Jonathan M. Scholey, and Erwin J. G. Peterman. Intraflagellar transport: mechanisms of motor action, cooperation, and cargo delivery. The FEBS Journal, 284:2905-2931, Sep 2017. URL: https://doi.org/10.1111/febs.14068, doi:10.1111/febs.14068. This article has 253 citations.
(prevo2017intraflagellartransportmechanisms pages 12-14): Bram Prevo, Jonathan M. Scholey, and Erwin J. G. Peterman. Intraflagellar transport: mechanisms of motor action, cooperation, and cargo delivery. The FEBS Journal, 284:2905-2931, Sep 2017. URL: https://doi.org/10.1111/febs.14068, doi:10.1111/febs.14068. This article has 253 citations.
(li2024regulationofciliary pages 3-5): Lin Li and Jie Ran. Regulation of ciliary homeostasis by intraflagellar transport-independent kinesins. Cell Death & Disease, Jan 2024. URL: https://doi.org/10.1038/s41419-024-06428-9, doi:10.1038/s41419-024-06428-9. This article has 21 citations and is from a peer-reviewed journal.
(prevo2017intraflagellartransportmechanisms pages 15-17): Bram Prevo, Jonathan M. Scholey, and Erwin J. G. Peterman. Intraflagellar transport: mechanisms of motor action, cooperation, and cargo delivery. The FEBS Journal, 284:2905-2931, Sep 2017. URL: https://doi.org/10.1111/febs.14068, doi:10.1111/febs.14068. This article has 253 citations.
(park2021cdklkinaseregulates pages 1-3): Kwangjin Park, Chunmei Li, Sofia Tsiropoulou, João Gonçalves, Christine Kondratev, Laurence Pelletier, Oliver E. Blacque, and Michel R. Leroux. Cdkl kinase regulates the length of the ciliary proximal segment. Current Biology, 31:2359-2373.e7, Jun 2021. URL: https://doi.org/10.1016/j.cub.2021.03.068, doi:10.1016/j.cub.2021.03.068. This article has 40 citations and is from a highest quality peer-reviewed journal.
(park2021cdklkinaseregulates pages 12-13): Kwangjin Park, Chunmei Li, Sofia Tsiropoulou, João Gonçalves, Christine Kondratev, Laurence Pelletier, Oliver E. Blacque, and Michel R. Leroux. Cdkl kinase regulates the length of the ciliary proximal segment. Current Biology, 31:2359-2373.e7, Jun 2021. URL: https://doi.org/10.1016/j.cub.2021.03.068, doi:10.1016/j.cub.2021.03.068. This article has 40 citations and is from a highest quality peer-reviewed journal.
(o’hagan2017glutamylationregulatestransport pages 4-5): Robert O’Hagan, Malan Silva, Ken C.Q. Nguyen, Winnie Zhang, Sebastian Bellotti, Yasmin H. Ramadan, David H. Hall, and Maureen M. Barr. Glutamylation regulates transport, specializes function, and sculpts the structure of cilia. Current biology : CB, 27:3430-3441.e6, Nov 2017. URL: https://doi.org/10.1016/j.cub.2017.09.066, doi:10.1016/j.cub.2017.09.066. This article has 119 citations.
(o’hagan2017glutamylationregulatestransport pages 1-3): Robert O’Hagan, Malan Silva, Ken C.Q. Nguyen, Winnie Zhang, Sebastian Bellotti, Yasmin H. Ramadan, David H. Hall, and Maureen M. Barr. Glutamylation regulates transport, specializes function, and sculpts the structure of cilia. Current biology : CB, 27:3430-3441.e6, Nov 2017. URL: https://doi.org/10.1016/j.cub.2017.09.066, doi:10.1016/j.cub.2017.09.066. This article has 119 citations.
(o’hagan2017glutamylationregulatestransport pages 7-8): Robert O’Hagan, Malan Silva, Ken C.Q. Nguyen, Winnie Zhang, Sebastian Bellotti, Yasmin H. Ramadan, David H. Hall, and Maureen M. Barr. Glutamylation regulates transport, specializes function, and sculpts the structure of cilia. Current biology : CB, 27:3430-3441.e6, Nov 2017. URL: https://doi.org/10.1016/j.cub.2017.09.066, doi:10.1016/j.cub.2017.09.066. This article has 119 citations.
(o’hagan2017glutamylationregulatestransport pages 9-10): Robert O’Hagan, Malan Silva, Ken C.Q. Nguyen, Winnie Zhang, Sebastian Bellotti, Yasmin H. Ramadan, David H. Hall, and Maureen M. Barr. Glutamylation regulates transport, specializes function, and sculpts the structure of cilia. Current biology : CB, 27:3430-3441.e6, Nov 2017. URL: https://doi.org/10.1016/j.cub.2017.09.066, doi:10.1016/j.cub.2017.09.066. This article has 119 citations.
(o’hagan2017glutamylationregulatestransport pages 9-9): Robert O’Hagan, Malan Silva, Ken C.Q. Nguyen, Winnie Zhang, Sebastian Bellotti, Yasmin H. Ramadan, David H. Hall, and Maureen M. Barr. Glutamylation regulates transport, specializes function, and sculpts the structure of cilia. Current biology : CB, 27:3430-3441.e6, Nov 2017. URL: https://doi.org/10.1016/j.cub.2017.09.066, doi:10.1016/j.cub.2017.09.066. This article has 119 citations.

Artifacts

Edison artifact artifact-00

Citations

verhey2011kinesinmotorsand pages 2-4
prevo2017intraflagellartransportmechanisms pages 33-35
nakayama2018ciliaryproteintrafficking pages 4-5
prevo2017intraflagellartransportmechanisms pages 12-14
li2024regulationofciliary pages 3-5
prevo2017intraflagellartransportmechanisms pages 15-17
park2021cdklkinaseregulates pages 1-3
park2021cdklkinaseregulates pages 12-13
https://doi.org/10.7282/t3cr5w7w,
https://doi.org/10.1093/jb/mvx087,
https://doi.org/10.1042/bst0391120,
https://doi.org/10.1111/febs.14068,
https://doi.org/10.1038/s41419-024-06428-9,
https://doi.org/10.1016/j.cub.2021.03.068,
https://doi.org/10.1016/j.cub.2017.09.066,

📚 Additional Documentation

Notes

(klp-20-notes.md)

klp-20 (C. elegans) — Gene Review Notes

Identity (verified from UniProt Q965T6)

UniProt: Q965T6 (KLP20_CAEEL), 646 aa, "Kinesin-like protein klp-20"
WormBase: WBGene00002230, sequence name Y50D7A.6, on Chromosome III
Family: TRAFAC class myosin-kinesin ATPase superfamily; Kinesin family; Kinesin II subfamily
Domain architecture (UniProt): N-terminal Kinesin motor domain (6–331) with the P-loop ATP-binding
Walker A (BINDING 91..98, ATP); a long coiled coil (342–552) stalk; a klp-11 interaction region
(525–550); and a disordered C-terminal tail (623–646, basic).
Structure: PDB 9IKB (X-ray 3.54 Å) covers residues 527–646 (the C-terminal stalk/tail); AlphaFoldDB Q965T6;
ComplexPortal CPX-1208 "Kinesin II motor complex".

klp-20 is one of the two motor subunits of heterotrimeric kinesin-II in C. elegans. Kinesin-II is the
heterotrimer KLP-11 + KLP-20 + KAP-1 (two distinct motor polypeptides + one non-motor accessory subunit KAP).
This is distinct from OSM-3, the homodimeric kinesin-2 that is the second anterograde IFT motor. klp-20 must be
kept distinct from its heterodimer partner klp-11 (KLP11_CAEEL) — much of the biochemistry was done on the
KLP-11/KLP-20 heterodimer, and where a result is specific to klp-11 alone I note it.

KNOWN (well supported)

Kinesin-II complex membership (experimental, klp-20-specific)

klp-20 is a subunit of the heterotrimeric kinesin-II motor. Purified recombinant kinesin-II behaves as a
monodisperse heterotrimer of the three named subunits:
PMID:17000880
PMID:17000880
The complex is the axonemal heterotrimeric kinesin-II complex (GO:0030993). UniProt SUBUNIT: "Component of the
kinesin II motor complex, a heterotrimeric complex composed of kap-1, klp-11 and klp-20" (UniProt Q965T6).
ComplexPortal CPX-1208 records the "Kinesin II motor complex" (NAS, PMID:20498083).

Microtubule motor / ATPase activity (experimental, complex-level)

Purified recombinant kinesin-II (containing klp-20) is an ATP-driven, microtubule plus-end-directed motor:
PMID:17000880
and, under optimized conditions, PMID:17000880.
Kinesin-II uses Mg-ATP by Michaelis–Menten kinetics:
PMID:17000880 and
PMID:17000880.
Kinesins are plus-end directed motors; anterograde IFT (base→ciliary tip) is toward MT plus ends, so the specific
MF is plus-end-directed microtubule motor activity (GO:0008574) rather than only the parent GO:0003777.
WormBase made the IDA GO:0003777 "microtubule motor activity" annotation from PMID:17000880.

Heterodimerization confers processivity; needed for cargo coupling (klp-20/klp-11 heterodimer)

The KLP-11/KLP-20 heterodimer is the functional unit: one motor domain is unprocessive alone but becomes
processive on heterodimerization:
PMID:20498083
Heterodimerization is required to bind KAP-1, which links the motor to cargo:
PMID:20498083
The unprocessive subunit contributes asymmetric autoregulation of motor activity:
[PMID:20498083 "The \"unprocessive\" subunit is kept in this partnership as it mediates an asymmetric autoregulation of the motor activity."]
UniProt (from PMID:20498083, PMID:21917588) elaborates: the C-termini of klp-20 and klp-11 form a coiled-coil
stalk necessary for association with kap-1, and prior to cargo binding the heterodimer is autoinhibited by its
tail folding onto the motor domain; cargo binding relieves autoinhibition. Interaction region on klp-20 = 525–550
(REGION, ECO:0000269|PubMed:21917588).

Anterograde IFT along sensory cilia (experimental at the pathway level)

In C. elegans amphid/phasmid sensory neuron cilia, kinesin-II and OSM-3 are the two anterograde IFT motors that
redundantly build the cilium foundation (middle/initial segment, MT doublets); OSM-3 alone extends the distal
singlet segment:
PMID:17000880
PMID:17000880
Kinesin-II is the slower motor (~0.5 µm/s in vivo) vs OSM-3 (~1.3 µm/s); the two act by mechanical competition,
with BBS proteins holding IFT-A and IFT-B together against the tension:
PMID:17000880
Subcellular location: UniProt SUBCELLULAR LOCATION = cilium (Cell projection), with a note that it localizes to the
base and transition zone of cilia (ECO:0000269|PubMed:28479320); also Cytoplasm/cytoskeleton (by similarity).

NOT established / KNOWLEDGE GAPS (for klp-20 specifically)

Which subunit of the heterodimer is the "unprocessive" one? PMID:20498083 shows the KLP-11/KLP-20 heterodimer
pairs a processive with an unprocessive motor domain and that the unprocessive subunit mediates asymmetric
autoregulation, but the abstract (only the abstract is cached; full text not available from PMC) does not, in the
cached text, assign the unprocessive/processive role to klp-20 vs klp-11 by name. So whether klp-20 itself is the
processive or the unprocessive head — and thus the residue-level basis of its individual duty ratio — is not
pinned down here. (Later biophysical work partly addresses this, but is not in our cache.)
klp-20-specific (vs klp-11-specific) contribution to autoinhibition / cargo release. UniProt annotates two
sites on klp-20 (444, 445) as "May be required for autoinhibition within the klp-11/klp-20 heterodimer"
(ECO:0000269|PubMed:20498083), but the mechanism by which klp-20 (as opposed to klp-11 or KAP-1) triggers
release of autoinhibition upon cargo binding is not resolved.
Direct ciliary cargo of the klp-20-containing motor. UniProt notes the kinesin-II complex delivers specific
ciliary cargo (e.g. che-3/dynein) to ciliary tips "likely mediated by IFT complexes A and B" (PMID:28479320) —
i.e. the direct, klp-20-motor-selected cargo repertoire is inferred through the IFT particle, not directly
enumerated for klp-20.

Annotation review plan (22 GOA rows)

MF:
- GO:0003777 microtubule motor activity — 3 rows (IBA GO_REF:0000033; IEA GO_REF:0000120; IDA PMID:17000880).
Core. IDA is the strongest; MF is really plus-end-directed. ACCEPT the IDA as core; the IBA/IEA are redundant
same-term support (KEEP_AS_NON_CORE / ACCEPT). Propose GO:0008574 as the more specific MF in core_functions.
- GO:0016887 ATP hydrolysis activity (IBA) — ACCEPT, part of motor mechanism (supported by PMID:17000880 kinetics).
- GO:0005524 ATP binding (IEA) — ACCEPT (Walker A motif present; molecular-mechanism support).
- GO:0008017 microtubule binding — 2 rows (IBA, IEA) — ACCEPT (motor must bind MT track).

CC:
- GO:0030993 axonemal heterotrimeric kinesin-II complex (IPI PMID:17000880) — ACCEPT, core complex membership.
- GO:0016939 kinesin II complex (NAS PMID:20498083) — ACCEPT, complex membership (more general than 0030993).
- GO:0005871 kinesin complex (IBA) — ACCEPT/KEEP_AS_NON_CORE (general parent of the above).
- GO:0032991 protein-containing complex (IEA ARBA) — over-general; MARK_AS_OVER_ANNOTATED (root-level).
- GO:0005929 cilium (IEA) — ACCEPT, location (consistent with UniProt SUBCELLULAR LOCATION cilium).
- GO:0005874 microtubule (IBA) — KEEP_AS_NON_CORE (track, not really a "location" of the protein per se).
- GO:0005737 cytoplasm (IBA) — KEEP_AS_NON_CORE (broad; consistent with cytoplasm-by-similarity).
- GO:0005856 cytoskeleton (IEA) — KEEP_AS_NON_CORE (general).
- GO:1904115 axon cytoplasm (IEA GO_REF:0000108, inferred from GO:0008089) — this is inferred solely from the
anterograde axonal transport BP, which itself is an IBA over-propagation (see below). klp-20 acts in sensory
cilia, not documented axonal transport in worm. MARK_AS_OVER_ANNOTATED / KEEP_AS_NON_CORE.

BP:
- GO:0035720 intraciliary anterograde transport (NAS PMID:20498083) — ACCEPT, core.
- GO:0060271 cilium assembly (IBA) — ACCEPT/KEEP_AS_NON_CORE (kinesin-II builds the cilium foundation; PMID:17000880).
- GO:0007018 microtubule-based movement — 3 rows (IBA; IEA; IDA PMID:17000880; NAS PMID:20498083 also) — ACCEPT
(parent of the specific transport; IDA strongest). Somewhat general vs 0035720.
- GO:0008089 anterograde axonal transport (IBA) — the phylogenetic transfer from KIF3/kinesin-II in neurons brings
in an axonal-transport term. In C. elegans the documented role is ciliary IFT, not classical axonal transport;
this is a likely IBA over-propagation. MARK_AS_OVER_ANNOTATED (or KEEP_AS_NON_CORE) — but do NOT remove the
underlying experimental terms; this is the electronic/IBA one only.

Kinesin modeling (per task): model motor via in_complex (GO:0030993 axonemal heterotrimeric kinesin-II complex) +
contributes_to_molecular_function (GO:0008574 plus-end-directed MT motor / GO:0016887 ATP hydrolysis), keeping a
specific MT motor MF (not protein binding). Directly_involved_in: GO:0035720 intraciliary anterograde transport,
GO:0060271 cilium assembly.

Deep research

falcon deep-research launched (foreground) with perplexity-lite fallback; see klp-20-deep-research-*.md if produced.
Primary review rests on the cached full text of PMID:17000880 and the abstract of PMID:20498083 plus UniProt Q965T6.

📄 View Raw YAML

id: Q965T6
gene_symbol: klp-20
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:6239
  label: Caenorhabditis elegans
description: >-
  klp-20 encodes one of the two motor subunits of heterotrimeric kinesin-II, the
  anterograde intraflagellar transport (IFT) motor of Caenorhabditis elegans. It is a
  member of the kinesin-2 subfamily with an N-terminal kinesin motor domain (P-loop
  ATPase) and a C-terminal coiled-coil stalk. klp-20 does not act alone: it
  heterodimerizes through its C-terminal stalk with the second motor subunit klp-11, and
  this heterodimer associates with the non-motor accessory subunit kap-1 to form the
  heterotrimeric kinesin-II holoenzyme (klp-11/klp-20/kap-1). Heterodimerization with
  klp-11 is required to generate a processive motor and to bind kap-1, which links the
  motor to IFT cargo. As part of kinesin-II the protein is an ATP-driven, microtubule
  plus-end-directed motor that, together with the homodimeric kinesin-2 motor osm-3,
  powers anterograde IFT along the middle (doublet) segment of sensory-neuron cilia,
  building and maintaining the ciliary axoneme. It localizes to sensory cilia, including
  the ciliary base and transition zone.
references:
  - id: GO_REF:0000002
    title: Gene Ontology annotation through association of InterPro records with GO terms
    findings: []
  - id: GO_REF:0000033
    title: Annotation inferences using phylogenetic trees
    findings: []
  - id: GO_REF:0000108
    title: Automatic assignment of GO terms using logical inference, based on on inter-ontology links
    findings: []
  - id: GO_REF:0000117
    title: Electronic Gene Ontology annotations created by ARBA machine learning models
    findings: []
  - id: GO_REF:0000120
    title: Combined Automated Annotation using Multiple IEA Methods
    findings: []
  - id: PMID:17000880
    title: Mechanism of transport of IFT particles in C. elegans cilia by the concerted action of kinesin-II and OSM-3 motors.
    findings:
      - statement: >-
          Purified recombinant kinesin-II behaves as a monodisperse heterotrimer of the
          KLP-11, KLP-20 and KAP-1 subunits (native mass ~287 kD, 1:1:1 stoichiometry),
          establishing klp-20 as a subunit of the heterotrimeric kinesin-II complex.
        supporting_text: "the KLP-11, KAP-1, and KLP-20 subunits elute as a monodisperse heterotrimeric complex"
        reference_section_type: RESULTS
      - statement: >-
          Kinesin-II (containing klp-20) is an ATP-driven microtubule motor; in gliding
          assays it moves microtubules and uses Mg-ATP by Michaelis-Menten kinetics.
        supporting_text: "indicating that Mg-ATP is the preferred substrate for kinesin-2 motors"
        reference_section_type: RESULTS
      - statement: >-
          Kinesin-II and OSM-3 are the two anterograde IFT motors that redundantly move
          IFT particles to build the sensory cilium foundation.
        supporting_text: "two anterograde IFT motors called kinesin-II and OSM-3"
        reference_section_type: INTRODUCTION
    reference_review:
      relevance: HIGH
      correctness: VERIFIED
      review_notes: >-
        Full text cached (PMC2064394). Directly names KLP-20 as a subunit of the purified
        heterotrimeric kinesin-II holoenzyme and characterizes its motor/ATPase activity
        and role in anterograde IFT. Source of the WormBase IDA (GO:0003777) and IPI
        (GO:0030993) annotations.
  - id: PMID:20498083
    title: Regulation of a heterodimeric kinesin-2 through an unprocessive motor domain that is turned processive by its partner.
    findings:
      - statement: >-
          The KLP-11/KLP-20 heterodimer pairs an unprocessive with a processive motor
          domain; heterodimerization generates processivity.
        supporting_text: "One motor domain is unprocessive as a homodimer"
        reference_section_type: ABSTRACT
      - statement: >-
          Heterodimerization of klp-20 with klp-11 is required to bind KAP-1, the in vivo
          link between the motor and its cargo.
        supporting_text: "heterodimerization is necessary to bind KAP1, the in vivo link between motor and"
        reference_section_type: ABSTRACT
    reference_review:
      relevance: HIGH
      correctness: VERIFIED
      review_notes: >-
        Abstract-only cache (full text not available from PMC2890855). Studies the
        C. elegans KLP-11/KLP-20 heterodimer directly; establishes that processivity and
        KAP-1 (cargo) binding require heterodimerization, and that the motor is
        autoregulated. Source of the ComplexPortal NAS annotations.
existing_annotations:
  - term:
      id: GO:0003777
      label: microtubule motor activity
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    qualifier: enables
    review:
      summary: >-
        Phylogenetic (IBA) support for microtubule motor activity, redundant with the
        experimental IDA below (PMID:17000880). Correct core molecular function of the
        kinesin motor domain. The more specific term is plus-end-directed microtubule
        motor activity (GO:0008574), captured in core_functions.
      action: ACCEPT
      supported_by:
        - reference_id: PMID:17000880
          supporting_text: "indicating that Mg-ATP is the preferred substrate for kinesin-2 motors"
          reference_section_type: RESULTS
  - term:
      id: GO:0005737
      label: cytoplasm
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    qualifier: is_active_in
    review:
      summary: >-
        Broad cytoplasmic localization consistent with UniProt (Cytoplasm, cytoskeleton by
        similarity), but uninformative relative to the specific ciliary localization. Keep
        as non-core context.
      action: KEEP_AS_NON_CORE
  - term:
      id: GO:0008017
      label: microtubule binding
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    qualifier: enables
    review:
      summary: >-
        Microtubule binding is intrinsic to the kinesin motor domain and required for the
        motor to engage its track. Correct and consistent with plus-end-directed motor
        activity; retained as a supporting molecular function.
      action: ACCEPT
  - term:
      id: GO:0060271
      label: cilium assembly
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    qualifier: involved_in
    review:
      summary: >-
        Kinesin-II (with klp-20 as a motor subunit) and osm-3 move IFT particles that
        redundantly build the sensory cilium foundation, so involvement in cilium assembly
        is well supported. Accept as a core biological process.
      action: ACCEPT
      supported_by:
        - reference_id: PMID:17000880
          supporting_text: "either motor but not both being dispensable for this function"
          reference_section_type: INTRODUCTION
  - term:
      id: GO:0005871
      label: kinesin complex
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    qualifier: part_of
    review:
      summary: >-
        Correct but general parent of the specific complex membership. klp-20 is a subunit
        of the (axonemal heterotrimeric) kinesin-II complex; the specific terms
        GO:0016939/GO:0030993 are preferred. Keep as non-core.
      action: KEEP_AS_NON_CORE
  - term:
      id: GO:0005874
      label: microtubule
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    qualifier: is_active_in
    review:
      summary: >-
        The microtubule is the motor's track rather than a distinct cellular location of
        the protein. Consistent with function but non-core; the informative location is the
        cilium.
      action: KEEP_AS_NON_CORE
  - term:
      id: GO:0016887
      label: ATP hydrolysis activity
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    qualifier: enables
    review:
      summary: >-
        ATP hydrolysis powers the kinesin motor; the motor domain of klp-20 contains the
        P-loop (Walker A) ATPase site, and purified kinesin-II shows Mg-ATP-dependent
        motility with Michaelis-Menten kinetics (PMID:17000880). Accept as part of the
        core motor mechanism.
      action: ACCEPT
      supported_by:
        - reference_id: PMID:17000880
          supporting_text: "kinesin-II–driven motility conformed to Michaelis-Menten kinetics"
          reference_section_type: RESULTS
  - term:
      id: GO:0008089
      label: anterograde axonal transport
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    qualifier: involved_in
    review:
      summary: >-
        This term is a phylogenetic transfer from kinesin-II orthologs (KIF3) that act in
        neuronal axonal transport. In C. elegans the documented role of klp-20/kinesin-II
        is anterograde intraflagellar (ciliary) transport, not classical axonal cargo
        transport; there is no experimental evidence for a klp-20 axonal-transport role in
        worm. Treated as an over-propagated electronic inference; the accurate specific
        term is intraciliary anterograde transport (GO:0035720).
      action: MARK_AS_OVER_ANNOTATED
      propagation_review:
        root_cause: TERM_SCOPING_PROBLEM
        failure_modes:
          - CONTEXT_OR_TISSUE_MISMATCH
          - GRANULARITY_MISMATCH
        source_entities:
          - source_id: FB:FBgn0004380
            source_label: Klp64D (Drosophila kinesin-II KIF3A ortholog)
            source_status: SUPPORTS_SOURCE_BUT_NOT_TARGET
            comment: >-
              Kinesin-II orthologs act in neuronal anterograde axonal transport, but the
              documented C. elegans klp-20 role is anterograde intraciliary transport, not
              axonal cargo transport; the axon-specific term does not transfer.
          - source_id: PANTHER:PTN000650181
            source_label: kinesin-2 anterograde-transport node
            source_status: SUPPORTS_SOURCE_BUT_NOT_TARGET
            comment: >-
              Node-level anterograde-transport inference; the ciliary (GO:0035720) rather
              than axonal (GO:0008089) child is the correct scoping for klp-20.
  - term:
      id: GO:0003777
      label: microtubule motor activity
    evidence_type: IEA
    original_reference_id: GO_REF:0000120
    qualifier: enables
    review:
      summary: >-
        Electronic (InterPro/ARBA) support for microtubule motor activity, redundant with
        the experimental IDA (PMID:17000880) and the IBA above. Correct core molecular
        function.
      action: ACCEPT
  - term:
      id: GO:0005524
      label: ATP binding
    evidence_type: IEA
    original_reference_id: GO_REF:0000002
    qualifier: enables
    review:
      summary: >-
        ATP binding via the conserved P-loop/Walker A motif of the kinesin motor domain
        (UniProt BINDING 91..98). Correct molecular-mechanism support for the ATP-driven
        motor; retained as supporting.
      action: ACCEPT
  - term:
      id: GO:0005856
      label: cytoskeleton
    evidence_type: IEA
    original_reference_id: GO_REF:0000120
    qualifier: located_in
    review:
      summary: >-
        General cytoskeletal localization from an electronic subcellular-location rule.
        Consistent with a microtubule motor but non-specific; the informative location is
        the cilium.
      action: KEEP_AS_NON_CORE
  - term:
      id: GO:0005929
      label: cilium
    evidence_type: IEA
    original_reference_id: GO_REF:0000120
    qualifier: located_in
    review:
      summary: >-
        Ciliary localization is well established: klp-20/kinesin-II functions in sensory
        cilia and UniProt records SUBCELLULAR LOCATION cilium (localizing to the base and
        transition zone; PMID:28479320). Accept as a core cellular location.
      action: ACCEPT
  - term:
      id: GO:0007018
      label: microtubule-based movement
    evidence_type: IEA
    original_reference_id: GO_REF:0000120
    qualifier: involved_in
    review:
      summary: >-
        Electronic support for microtubule-based movement, redundant with the experimental
        IDA (PMID:17000880). Correct but general; the specific process is intraciliary
        anterograde transport (GO:0035720). Accept.
      action: ACCEPT
  - term:
      id: GO:0008017
      label: microtubule binding
    evidence_type: IEA
    original_reference_id: GO_REF:0000002
    qualifier: enables
    review:
      summary: >-
        Electronic (InterPro) support for microtubule binding, redundant with the IBA
        above and intrinsic to the motor domain. Accept as supporting molecular function.
      action: ACCEPT
  - term:
      id: GO:0032991
      label: protein-containing complex
    evidence_type: IEA
    original_reference_id: GO_REF:0000117
    qualifier: part_of
    review:
      summary: >-
        Root-level complex membership from an ARBA rule. True (klp-20 is part of
        kinesin-II) but uninformative; the specific complex terms GO:0016939 and GO:0030993
        supersede it. Over-annotated at this level of generality.
      action: MARK_AS_OVER_ANNOTATED
  - term:
      id: GO:1904115
      label: axon cytoplasm
    evidence_type: IEA
    original_reference_id: GO_REF:0000108
    qualifier: located_in
    review:
      summary: >-
        Inferred logically (GO_REF:0000108) from the anterograde axonal transport
        annotation (GO:0008089), which is itself an over-propagated phylogenetic transfer.
        klp-20 acts in sensory cilia in C. elegans, not documented axoplasm; this location
        is a downstream consequence of the over-annotated axonal-transport term.
      action: MARK_AS_OVER_ANNOTATED
  - term:
      id: GO:0007018
      label: microtubule-based movement
    evidence_type: NAS
    original_reference_id: PMID:20498083
    qualifier: involved_in
    review:
      summary: >-
        ComplexPortal NAS annotation for microtubule-based movement, supported by the
        biophysical characterization of the KLP-11/KLP-20 heterodimer motor. Correct but
        general relative to intraciliary anterograde transport; accept.
      action: ACCEPT
      supported_by:
        - reference_id: PMID:20498083
          supporting_text: "One motor domain is unprocessive as a homodimer"
          reference_section_type: ABSTRACT
  - term:
      id: GO:0016939
      label: kinesin II complex
    evidence_type: NAS
    original_reference_id: PMID:20498083
    qualifier: part_of
    review:
      summary: >-
        klp-20 is a subunit of the kinesin II complex (the klp-11/klp-20/kap-1
        heterotrimer). Directly supported: heterodimerization of klp-20 with klp-11 is
        required to bind kap-1 (PMID:20498083), and the purified heterotrimer was
        characterized in PMID:17000880. Accept as core complex membership; the axonemal
        term GO:0030993 is the most specific.
      action: ACCEPT
      supported_by:
        - reference_id: PMID:20498083
          supporting_text: "heterodimerization is necessary to bind KAP1, the in vivo link between motor and"
          reference_section_type: ABSTRACT
  - term:
      id: GO:0035720
      label: intraciliary anterograde transport
    evidence_type: NAS
    original_reference_id: PMID:20498083
    qualifier: involved_in
    review:
      summary: >-
        Anterograde IFT is the core biological process of kinesin-II. As a kinesin-II motor
        subunit, klp-20 drives base-to-tip transport of IFT particles along sensory cilia
        together with osm-3. Accept as a core process.
      action: ACCEPT
      supported_by:
        - reference_id: PMID:17000880
          supporting_text: "two anterograde IFT motors called kinesin-II and OSM-3"
          reference_section_type: INTRODUCTION
  - term:
      id: GO:0003777
      label: microtubule motor activity
    evidence_type: IDA
    original_reference_id: PMID:17000880
    qualifier: enables
    review:
      summary: >-
        Direct experimental (IDA) annotation from characterization of purified kinesin-II,
        which contains klp-20 as one of its two motor subunits and moves microtubules in an
        ATP-dependent manner. This is the strongest evidence for the core molecular
        function. The most specific term is plus-end-directed microtubule motor activity
        (GO:0008574), used in core_functions.
      action: ACCEPT
      supported_by:
        - reference_id: PMID:17000880
          supporting_text: "the KLP-11, KAP-1, and KLP-20 subunits elute as a monodisperse heterotrimeric complex"
          reference_section_type: RESULTS
  - term:
      id: GO:0007018
      label: microtubule-based movement
    evidence_type: IDA
    original_reference_id: PMID:17000880
    qualifier: involved_in
    review:
      summary: >-
        Direct experimental annotation for microtubule-based movement from the kinesin-II
        gliding assays. Correct; general relative to intraciliary anterograde transport but
        experimentally solid. Accept.
      action: ACCEPT
      supported_by:
        - reference_id: PMID:17000880
          supporting_text: "indicating that Mg-ATP is the preferred substrate for kinesin-2 motors"
          reference_section_type: RESULTS
  - term:
      id: GO:0030993
      label: axonemal heterotrimeric kinesin-II complex
    evidence_type: IPI
    original_reference_id: PMID:17000880
    qualifier: part_of
    review:
      summary: >-
        Direct physical-interaction (IPI) evidence that klp-20 is a subunit of the axonemal
        heterotrimeric kinesin-II complex, purified as a monodisperse heterotrimer of
        KLP-11/KLP-20/KAP-1 (with WormBase klp-11 and kap-1 as the with/from partners).
        This is the most specific and best-supported complex-membership term and the core
        cellular-component annotation.
      action: ACCEPT
      supported_by:
        - reference_id: PMID:17000880
          supporting_text: "consisting of 1 mol each of its subunits KLP-11, KLP-20, and KAP-1 with a native molecular mass of 287 kD"
          reference_section_type: RESULTS
  - term:
      id: GO:0008574
      label: plus-end-directed microtubule motor activity
    evidence_type: IDA
    original_reference_id: PMID:17000880
    qualifier: enables
    review:
      summary: >-
        Proposed refinement of the experimental microtubule motor activity annotation
        (GO:0003777, IDA, PMID:17000880) to the more specific plus-end-directed microtubule
        motor activity. Kinesins are plus-end-directed motors and kinesin-II (with klp-20)
        drives anterograde (base-to-tip, plus-end-directed) IFT; the purified motor moves
        microtubules in gliding assays. This is the primary core molecular function.
      action: NEW
      supported_by:
        - reference_id: PMID:17000880
          supporting_text: "kinesin-II alone moved MTs at a maximal rate of 0.3"
          reference_section_type: RESULTS
core_functions:
  - description: >-
      As one of the two motor subunits of heterotrimeric kinesin-II (klp-11/klp-20/kap-1),
      klp-20 contributes to the ATP-driven, microtubule plus-end-directed motor activity of
      the complex. klp-20 heterodimerizes with klp-11 through its C-terminal coiled-coil
      stalk; this heterodimer is processive and binds the accessory subunit kap-1, which
      couples the motor to IFT cargo. The motor moves along the doublet microtubules of the
      sensory-cilium middle segment.
    molecular_function:
      id: GO:0008574
      label: plus-end-directed microtubule motor activity
    contributes_to_molecular_function:
      id: GO:0008574
      label: plus-end-directed microtubule motor activity
    in_complex:
      id: GO:0030993
      label: axonemal heterotrimeric kinesin-II complex
    directly_involved_in:
      - id: GO:0035720
        label: intraciliary anterograde transport
      - id: GO:0060271
        label: cilium assembly
    locations:
      - id: GO:0005929
        label: cilium
    supported_by:
      - reference_id: PMID:17000880
        supporting_text: "the KLP-11, KAP-1, and KLP-20 subunits elute as a monodisperse heterotrimeric complex"
        reference_section_type: RESULTS
      - reference_id: PMID:20498083
        supporting_text: "heterodimerization is necessary to bind KAP1, the in vivo link between motor and"
        reference_section_type: ABSTRACT
  - description: >-
      The kinesin motor domain of klp-20 hydrolyzes ATP to power microtubule-based
      movement. Purified kinesin-II (containing klp-20) uses Mg-ATP as its preferred
      substrate with Michaelis-Menten kinetics, and klp-20 carries the conserved P-loop
      (Walker A) ATP-binding motif.
    molecular_function:
      id: GO:0016887
      label: ATP hydrolysis activity
    contributes_to_molecular_function:
      id: GO:0016887
      label: ATP hydrolysis activity
    in_complex:
      id: GO:0030993
      label: axonemal heterotrimeric kinesin-II complex
    supported_by:
      - reference_id: PMID:17000880
        supporting_text: "indicating that Mg-ATP is the preferred substrate for kinesin-2 motors"
        reference_section_type: RESULTS
knowledge_gaps:
  - gap_statement: >-
      Within the klp-11/klp-20 heterodimer it is not resolved which subunit is the
      "unprocessive" motor domain and which is the processive one — i.e. whether klp-20
      itself is the processive or the autoinhibited/unprocessive head, and the
      residue-level basis of its individual duty ratio.
    boundary: >-
      It is established that heterodimerization of the two distinct C. elegans kinesin-2
      motor domains converts an otherwise unprocessive homodimer into a processive
      heterodimer, that the unprocessive subunit mediates an asymmetric autoregulation of
      motor activity, and that the heterodimer must form to bind kap-1 (the cargo link).
      UniProt annotates two klp-20 residues (444, 445) as possibly required for
      autoinhibition within the heterodimer.
    gap_kind:
      - BIOLOGY
    dark_aspect: RESIDUAL_SUBGAP
    status: OPEN
    significance: >-
      Kinesin-2 heterodimerization is the paradigm for how obligate motor heterodimers
      tune processivity and autoregulation; assigning the processive vs unprocessive role
      to klp-20 vs klp-11 defines the mechanistic division of labor of the anterograde IFT
      motor.
    resolution: >-
      Single-molecule processivity assays on defined homodimeric vs heterodimeric
      constructs of the klp-20 and klp-11 motor domains, with subunit-specific labeling and
      head-tracking to assign duty ratio to each subunit.
    provenance:
      - reference_id: PMID:20498083
        supporting_text: "One motor domain is unprocessive as a homodimer"
        reference_section_type: ABSTRACT
      - reference_id: PMID:20498083
        supporting_text: "asymmetric autoregulation of the motor"
        reference_section_type: ABSTRACT
  - gap_statement: >-
      The direct, klp-20-motor-selected ciliary cargo repertoire is not enumerated: what
      cargoes the klp-20-containing kinesin-II specifically delivers is inferred through the
      IFT-A/IFT-B particle rather than measured for the motor itself.
    boundary: >-
      Kinesin-II (with klp-20 as a motor subunit) and osm-3 are the two anterograde IFT
      motors that move IFT particles to build the sensory cilium foundation; kap-1 provides
      the in vivo link between the motor and cargo.
    gap_kind:
      - BIOLOGY
      - CURATION
    dark_aspect: BP_DARK
    status: OPEN
    significance: >-
      Defining the motor-specific cargo would clarify how the two anterograde IFT motors
      (kinesin-II vs osm-3) divide cargo responsibilities along the ciliary axoneme, which
      is central to understanding ciliogenesis and ciliopathy.
    resolution: >-
      Proximity labeling or cargo-trapping proteomics on the klp-20/kap-1 motor in cilia,
      combined with klp-20 loss-of-function IFT imaging to identify cargoes whose ciliary
      delivery specifically requires the klp-20-containing motor.
    provenance:
      - reference_id: PMID:20498083
        supporting_text: "heterodimerization is necessary to bind KAP1, the in vivo link between motor and"
        reference_section_type: ABSTRACT
suggested_questions:
  - question: >-
      Within the klp-11/klp-20 heterodimer, which motor domain is the processive one and
      which is unprocessive, and how do the two heads cooperate to set the ~0.5 um/s in vivo
      velocity of kinesin-II?
  - question: >-
      How does cargo binding to kap-1 relieve the tail-mediated autoinhibition of the
      klp-11/klp-20 heterodimer, and what is the specific contribution of the klp-20 tail
      (residues 444-445 and the 525-550 klp-11 interaction region)?
suggested_experiments:
  - description: >-
      Single-molecule motility (TIRF) comparison of purified klp-20 homodimer, klp-11
      homodimer, and klp-11/klp-20 heterodimer with subunit-specific fluorophores, to
      assign processivity and duty ratio to each subunit and test the
      asymmetric-autoregulation model.
    hypothesis: >-
      klp-20 and klp-11 have different intrinsic processivities, and one specific subunit
      is the unprocessive, autoregulatory head.
  - description: >-
      In vivo IFT imaging (kymography of fluorescently tagged IFT components) in klp-20
      loss-of-function versus osm-3 loss-of-function animals to define the cargoes and
      axonemal segments whose transport specifically depends on the klp-20-containing
      kinesin-II motor.
    hypothesis: >-
      The klp-20-containing kinesin-II motor is specifically required for anterograde
      transport of a defined subset of IFT cargoes along the middle (doublet) segment.
tags:
  - caeel-ciliopathy

klp-20

Gene Description

Existing Annotations Review

Core Functions

The kinesin motor domain of klp-20 hydrolyzes ATP to power microtubule-based movement. Purified kinesin-II (containing klp-20) uses Mg-ATP as its preferred substrate with Michaelis-Menten kinetics, and klp-20 carries the conserved P-loop (Walker A) ATP-binding motif.

References

Suggested Questions for Experts

Suggested Experiments

Knowledge Gaps

Tags

Deep Research

Falcon

Comprehensive Research Report: klp-20 (Kinesin-Like Protein 20) in Caenorhabditis elegans

1. Gene and Protein Identity

2. Molecular Function and Enzymatic Activity

3. Biological Function: Intraflagellar Transport (IFT)

3.1 Cooperation with OSM-3

3.2 Role in Ciliary Segment Assembly

4. Subcellular Localization

5. Mutant Phenotype and Genetic Redundancy

6. Regulation by Tubulin Post-Translational Modifications

7. Pathway Context and Broader Significance

8. Summary

Artifacts

Citations

📚 Additional Documentation

Notes

klp-20 (C. elegans) — Gene Review Notes

Identity (verified from UniProt Q965T6)

KNOWN (well supported)

Kinesin-II complex membership (experimental, klp-20-specific)

Microtubule motor / ATPase activity (experimental, complex-level)

Heterodimerization confers processivity; needed for cargo coupling (klp-20/klp-11 heterodimer)

Anterograde IFT along sensory cilia (experimental at the pathway level)

NOT established / KNOWLEDGE GAPS (for klp-20 specifically)

Annotation review plan (22 GOA rows)

Deep research

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