KLP-11 is one of the two motor (heavy-chain) subunits of Caenorhabditis elegans heterotrimeric kinesin-II, a plus-end-directed microtubule motor of the kinesin-2 family. The holoenzyme is a heterotrimer of the two distinct motor subunits KLP-11 and KLP-20 together with the non-motor accessory subunit KAP-1 (kinesin-associated protein), and is the nematode orthologue of vertebrate KIF3A/KIF3B/KAP3 kinesin-II. KLP-11 is unprocessive as a homodimer; processive movement requires heterodimerization with its partner KLP-20, and heterodimerization is also required to bind the KAP-1 cargo-adaptor subunit. Within the assembled motor, KLP-11 contributes microtubule plus-end motor and ATPase activity. Functionally, kinesin-II is one of two anterograde intraflagellar transport (IFT) motors in worm sensory cilia; together with the faster homodimeric OSM-3 (KIF17) motor it drives IFT particles along the doublet microtubules of the ciliary middle (initial) segment, with the two motors acting partly redundantly to build the cilium foundation. Kinesin-II moves comparatively slowly (~0.5 um/s) and, through mechanical competition with OSM-3, contributes to the tension across IFT particles that is regulated by BBS proteins. KLP-11 localizes to sensory cilia of ciliated neurons.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003777 microtubule motor activity | IBA GO_REF:0000033 | ACCEPT | Summary: KLP-11 is a kinesin-2 motor subunit that, as part of the KLP-11/KLP-20/KAP-1 heterotrimer, is an active plus-end-directed microtubule motor. The phylogenetic (IBA) annotation is well supported and corroborated by direct C. elegans data. Reason: Core molecular function. Kinesin-II motor activity is directly demonstrated for the purified holoenzyme containing KLP-11 (PMID:17000880). A more specific term (plus-end-directed microtubule motor activity) is captured in core_functions. Supporting Evidence: PMID:17000880 kinesin-II alone moved MTs at a maximal rate of 0.3 ΞΌm/s, and OSM-3 alone moved them at 0.7 ΞΌm/s |
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | ACCEPT | Summary: Generic cytoplasmic localization inferred phylogenetically. KLP-11 is present in the cytoplasm of ciliated neurons (cell bodies/dendrites) before and while operating in cilia, consistent with kinesin motors generally. Reason: Correct but low-specificity parent. The informative localization for KLP-11 is the cilium and the axonemal kinesin-II complex; retained as accurate context. |
| GO:0008017 microtubule binding | IBA GO_REF:0000033 | ACCEPT | Summary: Microtubule binding is an intrinsic property of the kinesin motor domain (FT 13..343) and is required for the motor activity of KLP-11-containing kinesin-II on axonemal microtubules. Reason: Well-supported; microtubule binding is a defining feature of kinesin motors and underpins the demonstrated MT gliding activity of kinesin-II (PMID:17000880). Supporting Evidence: PMID:17000880 the IFT particles assembling these sensory cilia are moved by the coordinate action of two anterograde IFT motors called kinesin-II and OSM-3, which are both members of the kinesin-2 family |
| GO:0030705 cytoskeleton-dependent intracellular transport | IBA GO_REF:0000033 | MODIFY | Summary: KLP-11 mediates microtubule-based (cytoskeleton-dependent) transport as part of kinesin-II. In the worm this is realized specifically as anterograde IFT within cilia. Reason: Correct but too general. The specific, experimentally supported process for KLP-11 is intraciliary anterograde transport; generalize the annotation to that term. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN009082057 Β· kinesin-2 / kinesin-II motor node SUPPORTS TRANSFER Proposed replacements: intraciliary anterograde transport Supporting Evidence: PMID:17000880 the IFT particles assembling these sensory cilia are moved by the coordinate action of two anterograde IFT motors called kinesin-II and OSM-3, which are both members of the kinesin-2 family |
| GO:0060271 cilium assembly | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Kinesin-II contributes to sensory cilium assembly by delivering IFT cargo along the middle segment. However, klp-11 single mutants have near-full-length cilia because OSM-3 acts redundantly in the middle segment and builds the distal segment, so KLP-11 is individually dispensable for ciliogenesis. Reason: The annotation is correct at the pathway level, but because of OSM-3 redundancy KLP-11 loss does not abolish cilium assembly; the sharpest core process is anterograde IFT. Retained as a real, non-core contribution. Supporting Evidence: PMID:17000880 These motors function redundantly to move the same IFT particles along the initial segment and build the cilium foundation, with either motor but not both being dispensable for this function PMID:17000880 OSM-6β·GFP moves at OSM-3's fast rate in klp-11 mutants |
| GO:0005871 kinesin complex | IBA GO_REF:0000033 | ACCEPT | Summary: KLP-11 is a subunit of a kinesin complex, specifically the heterotrimeric kinesin-II (KLP-11/KLP-20/KAP-1). The generic kinesin complex annotation is correct. Reason: Correct parent-level complex membership; the specific complex (kinesin II / axonemal heterotrimeric kinesin-II) is captured by the NAS/IPI annotations and core_functions. 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:0005874 microtubule | IBA GO_REF:0000033 | ACCEPT | Summary: KLP-11 is active on microtubules; as part of kinesin-II it translocates along the axonemal (doublet) microtubules of the ciliary middle segment. Reason: Correct localization/site-of-action for a microtubule motor, consistent with the demonstrated MT gliding activity of the holoenzyme. Supporting Evidence: PMID:17000880 kinesin-II alone moved MTs at a maximal rate of 0.3 ΞΌm/s, and OSM-3 alone moved them at 0.7 ΞΌm/s |
| GO:0007018 microtubule-based movement | IBA GO_REF:0000033 | ACCEPT | Summary: As a kinesin motor, KLP-11 drives microtubule-based movement. In the worm this is the anterograde movement of IFT particles within cilia. Reason: Correct general process; the specific term (intraciliary anterograde transport) is also annotated (NAS) and captured in core_functions. Supporting Evidence: PMID:17000880 the IFT particles assembling these sensory cilia are moved by the coordinate action of two anterograde IFT motors called kinesin-II and OSM-3, which are both members of the kinesin-2 family |
| GO:0016887 ATP hydrolysis activity | IBA GO_REF:0000033 | ACCEPT | Summary: KLP-11 contains a P-loop kinesin motor domain (ATP-binding site residues 99..106) and, as part of kinesin-II, hydrolyzes ATP to power motility; the holoenzyme uses Mg-ATP with Michaelis-Menten kinetics. Reason: ATP hydrolysis is essential for kinesin motor function and is directly evidenced by the ATP-dependent MT gliding kinetics of purified kinesin-II (PMID:17000880). Supporting Evidence: PMID:17000880 indicating that Mg-ATP is the preferred substrate for kinesin-2 motors |
| GO:0000166 nucleotide binding | IEA GO_REF:0000104 | ACCEPT | Summary: Broad nucleotide-binding parent inferred from the kinesin P-loop motif. KLP-11 binds ATP/ADP during its mechanochemical cycle. Reason: Correct but non-specific; the informative child (ATP binding) is separately annotated. |
| GO:0003774 cytoskeletal motor activity | IEA GO_REF:0000104 | ACCEPT | Summary: Parent of microtubule motor activity; correct for KLP-11 as a cytoskeletal (kinesin) motor. Reason: Correct but less specific than microtubule motor activity, which is separately annotated and refined in core_functions. |
| GO:0003777 microtubule motor activity | IEA GO_REF:0000120 | ACCEPT | Summary: InterPro/ARBA electronic assignment of microtubule motor activity based on the kinesin motor domain. Consistent with the IBA and IDA annotations. Reason: Correct; duplicates the well-supported microtubule motor activity from an electronic pipeline. |
| GO:0005524 ATP binding | IEA GO_REF:0000120 | ACCEPT | Summary: ATP binding at the kinesin motor domain P-loop (BINDING 99..106) is required for the ATPase-driven motor cycle of KLP-11. Reason: Correct and specific; supported by the conserved P-loop and the Mg-ATP kinetics of the holoenzyme (PMID:17000880). Supporting Evidence: PMID:17000880 indicating that Mg-ATP is the preferred substrate for kinesin-2 motors |
| GO:0005856 cytoskeleton | IEA GO_REF:0000120 | ACCEPT | Summary: KLP-11 localizes to the microtubule cytoskeleton (the ciliary axoneme). Broad but accurate. Reason: Correct low-specificity localization for a microtubule motor; the informative site is the cilium/axoneme. |
| GO:0005929 cilium | IEA GO_REF:0000120 | ACCEPT | Summary: KLP-11 localizes to sensory cilia, where kinesin-II performs anterograde IFT along the middle segment. Reason: Core localization, consistent with UniProt subcellular location and the cilia IFT role of kinesin-II (PMID:17000880). Supporting Evidence: PMID:17000880 the IFT particles assembling these sensory cilia are moved by the coordinate action of two anterograde IFT motors called kinesin-II and OSM-3, which are both members of the kinesin-2 family |
| GO:0007018 microtubule-based movement | IEA GO_REF:0000120 | ACCEPT | Summary: Electronic assignment of microtubule-based movement, duplicating the IBA/IDA process annotation. Reason: Correct; the more specific process (intraciliary anterograde transport) is also annotated. |
| GO:0008017 microtubule binding | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro electronic assignment of microtubule binding via the kinesin motor domain; duplicates the IBA annotation. Reason: Correct; microtubule binding is intrinsic to the kinesin motor domain. |
| GO:0032991 protein-containing complex | IEA GO_REF:0000117 | MODIFY | Summary: Generic complex-membership assignment. KLP-11 is specifically a subunit of the heterotrimeric kinesin-II complex. Reason: Too general. Replace with the specific kinesin II complex to convey the actual assembly KLP-11 belongs to. Proposed replacements: kinesin II complex 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:0007018 microtubule-based movement | NAS PMID:20498083 Regulation of a heterodimeric kinesin-2 through an unprocess... | ACCEPT | Summary: ComplexPortal NAS annotation. KLP-11 (as the KLP-11/KLP-20 heterodimer, and within the kinesin-II holoenzyme) drives microtubule-based movement; heterodimerization confers the processivity needed for transport. Reason: Author-stated (NAS) and consistent with the biochemistry: KLP-11 becomes a processive MT motor upon heterodimerization with KLP-20 (PMID:20498083). Supporting Evidence: PMID:20498083 KLP11/KLP20 of Caenorhabditis elegans cilia |
| GO:0016939 kinesin II complex | NAS PMID:20498083 Regulation of a heterodimeric kinesin-2 through an unprocess... | ACCEPT | Summary: KLP-11 is a subunit of kinesin II. The heterodimer of the two motor subunits (KLP-11/KLP-20) plus KAP-1 constitutes the kinesin-II complex; heterodimerization is required for KAP-1 binding. Reason: Core complex membership. Supported by both the ComplexPortal NAS record and the biochemistry of the KLP-11/KLP-20/KAP-1 assembly (PMID:20498083, PMID:17000880). Supporting Evidence: PMID:20498083 heterodimerization is necessary to bind KAP1, the in vivo link between 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:0035720 intraciliary anterograde transport | NAS PMID:20498083 Regulation of a heterodimeric kinesin-2 through an unprocess... | ACCEPT | Summary: KLP-11-containing kinesin-II is an anterograde IFT motor of C. elegans cilia; the heterodimeric motor drives anterograde transport of IFT particles. Reason: Core biological process for KLP-11. Author-stated (NAS) and corroborated by the cooperative anterograde IFT role of kinesin-II with OSM-3 (PMID:17000880). Supporting Evidence: PMID:17000880 the IFT particles assembling these sensory cilia are moved by the coordinate action of two anterograde IFT motors called kinesin-II and OSM-3, which are both members of the kinesin-2 family |
| GO:0003777 microtubule motor activity | IDA PMID:17000880 Mechanism of transport of IFT particles in C. elegans cilia ... | ACCEPT | Summary: Direct assay: purified recombinant C. elegans kinesin-II containing KLP-11 is an active microtubule motor in gliding assays, moving MTs at ~0.5 um/s. Reason: Direct experimental evidence (IDA) for KLP-11's core molecular function as a component of the kinesin-II motor holoenzyme. Supporting Evidence: PMID:17000880 kinesin-II alone moved MTs at a maximal rate of 0.3 ΞΌm/s, and OSM-3 alone moved them at 0.7 ΞΌm/s |
| GO:0007018 microtubule-based movement | IDA PMID:17000880 Mechanism of transport of IFT particles in C. elegans cilia ... | ACCEPT | Summary: Direct in vitro demonstration that KLP-11-containing kinesin-II generates microtubule-based movement (MT gliding), the biochemical basis of its IFT role. Reason: Direct experimental evidence (IDA). The specific process (intraciliary anterograde transport) is also annotated (NAS) and captured in core_functions. Supporting Evidence: PMID:17000880 kinesin-II alone moved MTs at a maximal rate of 0.3 ΞΌm/s, and OSM-3 alone moved them at 0.7 ΞΌm/s |
| GO:0030993 axonemal heterotrimeric kinesin-II complex | IPI PMID:17000880 Mechanism of transport of IFT particles in C. elegans cilia ... | ACCEPT | Summary: KLP-11 physically assembles into the axonemal heterotrimeric kinesin-II complex with KLP-20 (WBGene00002230) and KAP-1 (WBGene00002182), demonstrated as a monodisperse 1:1:1 (~287 kD) heterotrimer by sucrose gradients and gel filtration. Reason: Direct physical-interaction evidence (IPI) for the most specific, experimentally grounded cellular-component annotation for KLP-11. This is a core 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 |
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Download this section (compressed HTML)Q: What is the distinct mechanochemical role of the KLP-11 motor head versus the KLP-20 head within the heterodimer, and why is an unprocessive subunit retained?
Q: Which IFT-particle cargoes are engaged by kinesin-II via KAP-1 in C. elegans cilia, and how is the kinesin-II-to-OSM-3 handoff regulated along the middle segment?
Experiment: Reconstitute KLP-11/KLP-20 heterodimers and KLP-11 or KLP-20 homodimers and chimeras, and compare single-molecule processivity, velocity, and ATPase to dissect each head's contribution.
Hypothesis: KLP-11's head contributes asymmetric autoregulation but little autonomous processivity to kinesin-II.
Type: single-molecule motility / biochemistry
Experiment: Determine the cryo-EM structure of the intact KLP-11/KLP-20/KAP-1 heterotrimer in different nucleotide states and on microtubules.
Hypothesis: Full-length assembled kinesin-II adopts nucleotide-dependent conformations that impose asymmetric autoregulation.
Type: structural biology (cryo-EM)
What is not known β curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: No KLP-11 subunit-resolved in vivo molecular function is established independently of its partners: all motility, IFT and localization data are for the intact KLP-11/KLP-20/KAP-1 heterotrimer (or the KLP-11/KLP-20 heterodimer), and KLP-11 is unprocessive as a homodimer, so it has no demonstrated autonomous processive motor activity.
BIOLOGY MF_DARK
What is known: It is firmly established that KLP-11 is a subunit of the purified heterotrimeric kinesin-II holoenzyme, that the holoenzyme is an active plus-end MT motor, and that heterodimerization with KLP-20 is what confers processivity and enables KAP-1 binding.
Significance: Distinguishing the specific mechanochemical contribution of the KLP-11 head from that of KLP-20 is needed to understand why kinesin-II uses two distinct, asymmetric motor subunits.
What would resolve it: Single-molecule and structural analysis of engineered KLP-11 vs KLP-20 heads and chimeras, building on the finding that KLP-11 mediates asymmetric autoregulation of the heterodimer.
Provenance (the field's own admissions):
Gap: The identity of the IFT cargo(es) directly engaged by KLP-11-containing kinesin-II via KAP-1 in C. elegans, and how cargo loading/unloading is regulated along the middle segment, are not resolved by the primary literature reviewed here.
BIOLOGY BP_DARK
What is known: Kinesin-II is established as an anterograde IFT motor that moves IFT particles (IFT-A/IFT-B subcomplexes) along the middle segment, and heterodimerization is required for KAP-1 (the motor-cargo link) binding.
Significance: Defining the kinesin-II-specific cargo interface would clarify the division of labor between kinesin-II and OSM-3 and the handoff of IFT trains between motors.
What would resolve it: Proximity-labeling / cross-linking mass spectrometry of KAP-1 and KLP-11 in cilia, and cargo-selective transport assays.
Provenance (the field's own admissions):
Gap: The atomic structure of the fully assembled C. elegans kinesin-II heterotrimer and the structural basis of KLP-11-mediated asymmetric autoregulation of motor activity are unsolved.
BIOLOGY MF_DARK
What is known: Only a partial X-ray structure of the stalk/tail region (residues 537-782, PDB 9IKB, 3.54 A) of heterotrimeric kinesin-2 is available; the motor-domain interface and regulatory conformations are not resolved.
Significance: A full structure would explain how an unprocessive subunit is converted to a processive heterodimer and how autoregulation is imposed asymmetrically.
What would resolve it: Cryo-EM / higher-resolution crystallography of the intact KLP-11/KLP-20/KAP-1 holoenzyme in defined nucleotide states.
Provenance (the field's own admissions):
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