mhcA

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0005737 cytoplasm	IBA GO_REF:0000033	ACCEPT	Summary: Phylogenetic inference that myosin II acts in the cytoplasm. Correct and well supported by direct evidence, though not the most informative localization for this cortical motor. Reason: Myosin II is a cytoplasmic/cortical protein; the general cytoplasm term is correct but subordinate to the more specific cell cortex and cleavage furrow localizations captured elsewhere. Supporting Evidence: PMID:2578450 If ATP is present, 98% of that myosin is released
GO:0000146 microfilament motor activity	IBA GO_REF:0000033	ACCEPT	Summary: Phylogenetic inference of actin-based motor activity, the defining molecular function of a conventional myosin heavy chain. Reason: Directly demonstrated for the Dictyostelium myosin II head, which is an actin-activated ATPase that supports actin filament sliding. This is a core molecular function. Supporting Evidence: PMID:2530629 displayed actin-activated adenosine triphosphatase activity
GO:0051015 actin filament binding	IBA GO_REF:0000033	ACCEPT	Summary: Phylogenetic inference of actin filament binding, an integral part of the myosin motor cycle. Reason: The Dictyostelium myosin II motor domain binds actin filaments directly; loop-4 and cleft mutations that weaken actin binding have been characterized. Core function. Supporting Evidence: PMID:18067324 loop 4 is a functional actin-binding region that stabilizes actomyosin
GO:0016460 myosin II complex	IBA GO_REF:0000033	ACCEPT	Summary: Phylogenetic inference that the heavy chain is part of the myosin II hexameric complex. Reason: mhcA is the heavy chain of the two-headed myosin II hexamer (2 heavy, 2 essential and 2 regulatory light chains). Core assignment. Supporting Evidence: PMID:15492777 forms bipolar thick filament (BTF) structures
GO:0032982 myosin filament	IBA GO_REF:0000033	ACCEPT	Summary: Phylogenetic inference that myosin II is active in myosin (thick) filaments. Reason: Myosin II self-assembles into bipolar thick filaments that are the functional force-generating unit. Core assignment. Supporting Evidence: PMID:15492777 assembles in a regulated manner similar to full-length myosin-II and
GO:0003774 cytoskeletal motor activity	IEA GO_REF:0000002	ACCEPT	Summary: InterPro2GO inference of cytoskeletal motor activity from the myosin motor domain. Reason: Parent term of microfilament motor activity; correct for the actin-based myosin II motor. Supporting Evidence: PMID:2530629 displayed actin-activated adenosine triphosphatase activity
GO:0005524 ATP binding	IEA GO_REF:0000002	ACCEPT	Summary: InterPro2GO inference of ATP binding from the P-loop of the myosin motor domain. Reason: The myosin motor domain has a canonical ATP-binding P-loop and hydrolyzes ATP to power the motor. Core function. Supporting Evidence: PMID:2530629 displayed actin-activated adenosine triphosphatase activity
GO:0005737 cytoplasm	IEA GO_REF:0000117	ACCEPT	Summary: ARBA electronic annotation of cytoplasmic localization. Correct. Reason: Myosin II is cytoplasmic/cortical; consistent with direct evidence. Supporting Evidence: PMID:2578450 contain nearly half of the cell's myosin
GO:0005938 cell cortex	IEA GO_REF:0000044	ACCEPT	Summary: UniProt subcellular-location electronic annotation of cell cortex localization, matching the documented enrichment in the posterior cortex. Reason: Myosin II is highly enriched in the cell cortex, particularly the posterior cortex of migrating cells. Core localization. Supporting Evidence: PMID:16461463 Highly enriched in the cell cortex, actin, myosin II
GO:0016459 myosin complex	IEA GO_REF:0000002	ACCEPT	Summary: InterPro2GO inference that the heavy chain is part of a myosin complex. Reason: Correct but general; the more specific myosin II complex is the accurate assignment for this class II heavy chain. Supporting Evidence: PMID:15492777 forms bipolar thick filament (BTF) structures
GO:0031143 pseudopodium	IEA GO_REF:0000117	KEEP AS NON CORE	Summary: ARBA electronic annotation of pseudopodium localization, corroborated by live-imaging showing transient myosin enrichment in retracting pseudopods. Reason: Myosin II transiently concentrates in the tips of retracting pseudopods, but its predominant and functionally central localization is the posterior cortex and cleavage furrow. Supporting Evidence: PMID:8552657 increases transiently in the tips of retracting pseudopods
GO:0031152 aggregation involved in sorocarp development	IEA GO_REF:0000117	MARK AS OVER ANNOTATED	Summary: ARBA electronic annotation of a role in aggregation. Myosin-null cells still aggregate, so involvement in the aggregation step itself is overstated by this electronic inference. Reason: Genetic ablation of mhcA blocks development at a later (post-aggregation) stage; myosin-null (hmm) cells can still aggregate. The requirement is at culmination, not aggregation, so annotation to the aggregation step over-reaches. Supporting Evidence: PMID:3576222 blocked at a later stage in the Dictyostelium
GO:0031270 pseudopodium retraction	IEA GO_REF:0000117	ACCEPT	Summary: ARBA electronic annotation of a role in pseudopodium retraction, supported experimentally by traction-force imaging of retracting pseudopods. Reason: Accumulated filamentous myosin II generates the contractile force that retracts pseudopodia and the cell rear during migration. Supporting Evidence: PMID:18388319 the source of the retraction force is the motor activity of accumulated myosin
GO:0048870 cell motility	IEA GO_REF:0000117	KEEP AS NON CORE	Summary: ARBA electronic annotation of a role in cell motility. Reason: Myosin II contributes to amoeboid motility (rear retraction, cortical tension, bleb-based movement) but is not strictly required for all forms of locomotion; it is a modulator rather than the propulsive engine. Supporting Evidence: PMID:25887420 the cytoskeletal genes abpA or mhcA, which are also required for motility
GO:0051015 actin filament binding	IEA GO_REF:0000002	ACCEPT	Summary: InterPro2GO inference of actin filament binding from the myosin motor domain. Consistent with direct biochemical evidence. Reason: The myosin II motor domain binds actin filaments directly. Core function. Supporting Evidence: PMID:18067324 loop 4 is a functional actin-binding region that stabilizes actomyosin
GO:0005515 protein binding	IPI PMID:18725645 Actin-binding cleft closure in myosin II probed by site-dire...	KEEP AS NON CORE	Summary: Bare protein binding from an EPR/spin-labeling study of the myosin actin-binding cleft. Uninformative term; the interaction assayed is myosin-actin. Reason: The generic protein binding term conveys little; the underlying interaction is actin binding by the myosin motor, already captured by the actin filament binding annotations. Supporting Evidence: PMID:18725645 closure of the actin-binding cleft of myosin
GO:0005515 protein binding	IPI PMID:18854143 An Elmo-like protein associated with myosin II restricts spu...	KEEP AS NON CORE	Summary: Protein binding reflecting the physical association of myosin II with the Elmo-like protein ElmoA at the cortex. Reason: A real interaction (ElmoA associates with cortical actin and myosin II) but the bare protein binding term is uninformative; the specific partner is noted here. Supporting Evidence: PMID:18854143 ElmoA associates with cortical actin and myosin II
GO:0005515 protein binding	IPI PMID:18971336 Visualizing myosin-actin interaction with a genetically-enco...	KEEP AS NON CORE	Summary: Protein binding derived from a genetically-encoded strain sensor visualizing the myosin II-F-actin interaction. Reason: The interaction assayed is myosin-actin, already captured by actin filament binding; the generic protein binding term adds no specific information. Supporting Evidence: PMID:18971336 visualize the interaction between myosin II and F-actin in Dictyostelium cells
GO:0005515 protein binding	IPI PMID:20351242 Myosin complexed with ADP and blebbistatin reversibly adopts...	KEEP AS NON CORE	Summary: Protein binding from a biophysical study of the myosin.ADP.blebbistatin complex probing actin binding and lever priming. Reason: The assayed interaction is myosin-actin under a pharmacological probe; the bare protein binding term is uninformative and subordinate to the actin-binding and motor annotations. Supporting Evidence: PMID:20351242 blebbistatin does not weaken the tight actin binding of myosin
GO:0042802 identical protein binding	IPI PMID:15492777 Dictyostelium myosin bipolar thick filament formation: impor...	ACCEPT	Summary: Self-association of myosin heavy chains through tail-tail interactions to build bipolar thick filaments. Reason: Myosin II self-assembles into bipolar thick filaments via homotypic coiled-coil tail interactions; identical protein binding captures this core self-assembly activity. Supporting Evidence: PMID:15492777 forms bipolar thick filament (BTF) structures
GO:0005515 protein binding	IPI PMID:41353402 Talin force coupling underlies eukaryotic cell-substrate adh...	UNDECIDED	Summary: Protein binding annotation arising from a study of talin-A force coupling in amoeboid cells. The abstract does not detail a direct myosin-partner interaction, and full text was not verified here. Reason: Cannot verify the specific myosin II interaction claimed from the available text; the paper focuses on talin/SibA force coupling. Per policy, an unverifiable experimental interaction is left undecided rather than accepted or removed.
GO:0044351 macropinocytosis	IMP PMID:41332277 The RNA-binding protein RNP1A is essential and interacts wit...	KEEP AS NON CORE	Summary: Myosin II is a component of cytoplasmic contractility kits whose loss affects cell mechanics and macropinocytosis-related processes. Reason: Myosin II contributes to cortical mechanics underlying macropinocytic cup dynamics, but macropinocytosis is a downstream cellular process rather than the core motor function. Supporting Evidence: PMID:41332277 myosin II, cortexillin I and IQGAP1 assemble in the cytoplasm into
GO:0140350 inchworm-type cell migration	IMP PMID:40712579 Inchworm migration facilitates amoeboid cell adaptation to h...	KEEP AS NON CORE	Summary: On highly adhesive surfaces Dictyostelium switches to inchworm migration that repurposes the cytokinesis (actomyosin) machinery, of which myosin II is central. Reason: Myosin II-based contractility is redeployed for this specialized migration mode; it is a context-specific behavior rather than a core molecular function. Supporting Evidence: PMID:40712579 the repurposing of cytokinesis machinery for migration mode shifting
GO:0000915 actomyosin contractile ring assembly	IMP PMID:40712579 Inchworm migration facilitates amoeboid cell adaptation to h...	KEEP AS NON CORE	Summary: Assembly of the contractile actomyosin ring/machinery, which incorporates myosin II, is invoked during inchworm migration and cytokinesis. Reason: Myosin II is a required component of the actomyosin contractile ring; here the term is applied in the migration context. Genuine but secondary to the cytokinesis role captured by the core function. Supporting Evidence: PMID:40712579 the repurposing of cytokinesis machinery for migration mode shifting
GO:0001931 uropod	IDA PMID:17126332 Time-resolved responses to chemoattractant, characteristic o...	ACCEPT	Summary: Filamentous myosin II is recruited to the rear (tail/uropod) of chemotaxing cells. Reason: The cell tail is specified by recruitment of filamentous myosin-II; uropod localization is well documented and functionally important for rear retraction. Supporting Evidence: PMID:17126332 the tail by the recruitment of filamentous myosin-II
GO:0000281 mitotic cytokinesis	IMP PMID:10588668 LvsA, a protein related to the mouse beige protein, is requi...	ACCEPT	Summary: Myosin II localizes to the cleavage furrow and is required for furrow-based cytokinesis; studied here in the context of the LvsA cytokinesis mutant. Reason: Myosin II accumulation at the cleavage furrow drives the contractile ring; this is a core cellular role of mhcA. Supporting Evidence: PMID:10588668 they initiate furrow formation with concomitant myosin II localization at the
GO:0000281 mitotic cytokinesis	IGI PMID:19065153 Cell adhesion molecules regulate contractile ring-independen...	ACCEPT	Summary: Genetic interaction showing mhcA (myosin II) contributes to contractile-ring-dependent cytokinesis, with adhesion molecules covering a parallel ring-independent pathway. Reason: Double knockouts of mhcA with paxB or vinA have more severe cytokinesis defects, confirming myosin II's role in furrow-based division. Core role. Supporting Evidence: PMID:19065153 Double knockout strains lacking mhcA, which codes for myosin II
GO:0000281 mitotic cytokinesis	IMP PMID:2721503 Gene replacement in Dictyostelium: generation of myosin null...	ACCEPT	Summary: Myosin-null mutants generated by gene replacement fail normal cell division in suspension, providing genetic proof of the cytokinesis requirement. Reason: Elimination of the conventional myosin gene abolishes normal cell division in suspension. Core cellular role. Supporting Evidence: PMID:2721503 the conventional myosin gene is required for growth in suspension, normal
GO:0000281 mitotic cytokinesis	IMP PMID:3576222 Disruption of the Dictyostelium myosin heavy chain gene by h...	ACCEPT	Summary: Disruption of the myosin heavy chain gene produces multinucleate cells defective in cytokinesis, the classic genetic proof of myosin II's role. Reason: hmm cells defective in cytokinesis become large and multinucleate; genetic proof that intact myosin is required for cytokinesis. Core role. Supporting Evidence: PMID:3576222 genetic proof that the intact myosin molecule is required for cytokinesis
GO:0006930 substrate-dependent cell migration, cell extension	IDA PMID:37987147 Adaptive pathfinding by nucleokinesis during amoeboid migrat...	KEEP AS NON CORE	Summary: Amoeboid migration/pathfinding involving nucleokinesis; myosin II contributes to the contractile forces that reposition the cell body and nucleus. Reason: Myosin II-driven cortical contractility participates in amoeboid migration and cell extension/retraction, but this migratory behavior is downstream of the core motor function. Supporting Evidence: PMID:18388319 the source of the retraction force is the motor activity of accumulated myosin
GO:0006935 chemotaxis	IMP PMID:16926192 Dissection of amoeboid movement into two mechanically distin...	KEEP AS NON CORE	Summary: Myosin II is required for bleb-based leading-edge protrusion and rear retraction that contribute to efficient chemotactic movement. Reason: Myosin II contributes to chemotactic locomotion (bleb formation, cell body retraction), but chemotaxis is an integrated cellular behavior rather than the core molecular function. Supporting Evidence: PMID:16926192 reduced under conditions that prevent blebbing
GO:0008360 regulation of cell shape	IMP PMID:8874966 Dictyostelium cell shape generation requires myosin II.	ACCEPT	Summary: Myosin II is required for generating and maintaining three-dimensional cell shape independent of the substrate. Reason: Cells lacking myosin II cannot generate or maintain 3D shape and become spherical in suspension; cortical-tension-based shape control is a central myosin II function. Supporting Evidence: PMID:8874966 3D cell shape generation requires myosin II
GO:0009612 response to mechanical stimulus	IMP PMID:23442953 Myosin-II-mediated directional migration of Dictyostelium ce...	KEEP AS NON CORE	Summary: Myosin II accumulates at sites of mechanical strain during cyclic substrate stretching, mediating directional responses. Reason: Myosin II participates in the cellular response to mechanical stimuli by accumulating where strain is received; this mechanoresponsive behavior is secondary to its motor/contractile function. Supporting Evidence: PMID:23442953 Dictyostelium cells accumulate myosin II at the portion of the cell where a
GO:0030038 contractile actin filament bundle assembly	IMP PMID:15894626 Subsecond reorganization of the actin network in cell motili...	UNDECIDED	Summary: This paper analyzes subsecond actin-network reorganization and bundle formation but does not, in the available abstract, establish a myosin II requirement; full text was not verified. Reason: The cited abstract concerns actin filament growth and bundling dynamics and does not describe a myosin II perturbation. Unable to verify the basis of this annotation from available text.
GO:0030837 negative regulation of actin filament polymerization	IMP PMID:15894626 Subsecond reorganization of the actin network in cell motili...	UNDECIDED	Summary: A role for myosin II in negatively regulating actin polymerization is not established by the available abstract, which focuses on actin-network dynamics. Reason: Cannot verify a myosin II perturbation or a direct role in limiting actin polymerization from the cited text; left undecided per policy.
GO:0031152 aggregation involved in sorocarp development	IEP PMID:25887420 Leaps and lulls in the developmental transcriptome of Dictyo...	MARK AS OVER ANNOTATED	Summary: Expression-based association; mhcA is a cytoskeletal gene differentially regulated during development. Myosin-null cells nonetheless still aggregate, so involvement in the aggregation step is overstated. Reason: IEP reflects developmental expression rather than a specific requirement for aggregation; myosin-null cells still aggregate and are blocked later, at culmination. Annotation to the aggregation step over-reaches. Supporting Evidence: PMID:25887420 the cytoskeletal genes abpA or mhcA, which are also required for motility
GO:0031154 culmination involved in sorocarp development	IMP PMID:2721503 Gene replacement in Dictyostelium: generation of myosin null...	ACCEPT	Summary: Myosin-null mutants are defective in later multicellular development (sporogenesis), consistent with a requirement at culmination. Reason: The conventional myosin gene is required for sporogenesis; myosin II contractility is needed for the morphogenetic cell movements of culmination. Supporting Evidence: PMID:2721503 cell division and sporogenesis
GO:0031154 culmination involved in sorocarp development	IMP PMID:3576222 Disruption of the Dictyostelium myosin heavy chain gene by h...	ACCEPT	Summary: Myosin heavy chain disruption blocks development at a late stage after aggregation, consistent with a culmination defect. Reason: hmm (myosin-null) cells aggregate but are blocked later in the developmental cycle, indicating a requirement in culmination/morphogenesis. Supporting Evidence: PMID:3576222 blocked at a later stage in the Dictyostelium
GO:0031270 pseudopodium retraction	IMP PMID:18388319 Actin-based propulsive forces and myosin-II-based contractil...	ACCEPT	Summary: Motor activity of accumulated filamentous myosin II generates the contractile forces that retract pseudopodia. Reason: Direct force-microscopy evidence that myosin II motor activity is the source of retraction force in pseudopodia; a central role in rear/tail dynamics during migration. Supporting Evidence: PMID:18388319 the source of the retraction force is the motor activity of accumulated myosin
GO:0033298 contractile vacuole organization	IMP PMID:19843280 Roles of an unconventional protein kinase and myosin II in a...	KEEP AS NON CORE	Summary: The cortical myosin II cytoskeleton contributes to periodic contractions and discharge of the contractile vacuole; myosin-null cells have enlarged, dysfunctional vacuoles. Reason: Myosin II supports contractile-vacuole dynamics as part of its general cortical contractile role; a legitimate but non-core cellular function. Supporting Evidence: PMID:19843280 myosin II null cells also results in enlarged CVs with impaired dynamics
GO:0034461 uropod retraction	IMP PMID:18388319 Actin-based propulsive forces and myosin-II-based contractil...	ACCEPT	Summary: Accumulated myosin II generates the contractile traction that retracts the cell rear/uropod during migration. Reason: Myosin II motor activity provides the rear-retraction force documented by simultaneous imaging of GFP-myosin II and traction forces. Core migratory role. Supporting Evidence: PMID:18388319 the source of the retraction force is the motor activity of accumulated myosin
GO:0046847 filopodium assembly	IMP PMID:15855234 Computer-assisted analysis of filopod formation and the role...	KEEP AS NON CORE	Summary: Myosin II heavy chain phosphorylation state modulates filopod formation during migration and chemotaxis. Reason: Regulated myosin II (via MHC phosphorylation) influences filopod formation, but filopodium assembly is primarily an actin-driven process that myosin II modulates rather than directly executes. Supporting Evidence: PMID:15855234 MHC phosphorylation-dephosphorylation plays a role in the regulation of filopod
GO:0050982 detection of mechanical stimulus	IMP PMID:22379107 A mechanosensory system governs myosin II accumulation in di...	ACCEPT	Summary: Myosin II, together with cortexillin I, forms the core cortical mechanosensor that detects and responds to mechanical stress. Reason: Myosin II is a direct constituent of the mechanosensory module that accumulates in response to applied mechanical stress; mechanosensation is an established myosin II activity in this organism. Supporting Evidence: PMID:22379107 the mechanoenzyme myosin II and the actin cross-linker cortexillin I form a
GO:0005515 protein binding	IPI PMID:36165849 The lectin Discoidin I acts in the cytoplasm to help assembl...	KEEP AS NON CORE	Summary: Protein binding reflecting myosin II's participation in cytoplasmic contractility kits alongside Discoidin I, cortexillin I and IQGAP. Reason: A real assembly-level interaction, but the generic protein binding term is uninformative; the specific contractility-kit context is noted here. Supporting Evidence: PMID:36165849 the contractility machinery organizes into higher order assemblies termed
GO:0140220 pathogen-containing vacuole	HDA PMID:18980612 Proteome analysis of Legionella vacuoles purified by magneti...	KEEP AS NON CORE	Summary: Myosin II was detected among hundreds of host proteins in a proteomic analysis of purified Legionella-containing vacuoles. Reason: Detection in a whole-vacuole proteome likely reflects cortical/cytoplasmic myosin II associated with the phagosomal membrane rather than a dedicated vacuolar function; retained as non-core, peripheral association. Supporting Evidence: PMID:18980612 revealed 566 host proteins
GO:0000146 microfilament motor activity	IDA PMID:2530629 Expression and characterization of a functional myosin head ...	ACCEPT	Summary: The isolated recombinant myosin head fragment displays actin-activated ATPase activity and supports actin filament sliding in vitro. Reason: Direct demonstration of the core actin-based motor activity of the Dictyostelium myosin II head. Supporting Evidence: PMID:2530629 displayed actin-activated adenosine triphosphatase activity
GO:0005829 cytosol	IDA PMID:23132928 Delineating the core regulatory elements crucial for directe...	ACCEPT	Summary: Myosin II is present in the cytosol (soluble/disassembled pool), from which it assembles onto the cortex. Reason: A substantial fraction of myosin II is soluble/cytosolic and is released from the cytoskeleton in the presence of ATP; cytosolic localization is correct though subordinate to cortical localization. Supporting Evidence: PMID:2578450 If ATP is present, 98% of that myosin is released
GO:0016460 myosin II complex	IDA PMID:4278009 Biochemical and structural studies of actomyosin-like protei...	ACCEPT	Summary: Classic biochemical isolation and characterization of Dictyostelium myosin, establishing the actomyosin-like myosin II complex. Reason: The heavy chain is the core subunit of the isolated myosin II complex. Supporting Evidence: PMID:4278009 Isolation and characterization of myosin from amoebae of Dictyostelium
GO:0031012 extracellular matrix	HDA PMID:26152465 Proteomic profiling of the extracellular matrix (slime sheat...	MARK AS OVER ANNOTATED	Summary: Myosin II was identified in a proteomic profile of the slug extracellular matrix (slime sheath). Reason: Myosin II is an intracellular cortical motor; its detection in a slime-sheath proteome most likely reflects cytoplasmic contamination during ECM preparation rather than a genuine extracellular-matrix localization. Supporting Evidence: PMID:26152465 An LC/MS/MS analysis of slug ECM revealed the presence of a large number of
GO:0031143 pseudopodium	IDA PMID:8552657 Myosin dynamics in live Dictyostelium cells.	KEEP AS NON CORE	Summary: Live-cell GFP-myosin imaging shows transient myosin II enrichment in the tips of retracting pseudopods. Reason: Genuine but transient localization; myosin II's principal functional sites are the posterior cortex and cleavage furrow. Supporting Evidence: PMID:8552657 increases transiently in the tips of retracting pseudopods
GO:0031254 cell trailing edge	IDA PMID:22114350 Actin cross-linking proteins cortexillin I and II are requir...	ACCEPT	Summary: Myosin II is enriched at the rear/trailing edge (posterior cortex) of migrating cells. Reason: Posterior/trailing-edge enrichment of myosin II is a hallmark of its role in rear retraction during directed migration. Supporting Evidence: PMID:8552657 posterior cortex of migrating cells
GO:0031410 cytoplasmic vesicle	IDA PMID:3243031 Electron microscopic localization of myosin II and ABP-120 i...	KEEP AS NON CORE	Summary: Immuno-EM localizes a fraction of myosin II to unidentified cytoplasmic vesicles in addition to cortical filament arrays. Reason: A minor documented localization; peripheral to the core cortical contractile function. Supporting Evidence: PMID:3243031 with unidentified cytoplasmic vesicles
GO:0032009 early phagosome	IDA PMID:20200225 A myosin IK-Abp1-PakB circuit acts as a switch to regulate p...	KEEP AS NON CORE	Summary: Myosin II is part of the concentric protein rings of the phagocytic furrow/cup during particle engulfment. Reason: Myosin II localizes to the phagocytic furrow together with MyoK, Abp1, Arp3 and coronin; a genuine but non-core localization reflecting cortical contractility during phagocytosis. Supporting Evidence: PMID:20200225 concentric overlapping rings of MyoK, Abp1, Arp3, coronin, and myosin II
GO:0032154 cleavage furrow	IDA PMID:19515202 PTEN is a mechanosensing signal transducer for myosin II loc...	ACCEPT	Summary: Myosin II co-localizes with PTEN at the furrow region of dividing cells. Reason: Cleavage-furrow localization of myosin II is central to its cytokinesis function. Core localization. Supporting Evidence: PMID:19515202 region of dividing cells
GO:0032154 cleavage furrow	IDA PMID:8552657 Myosin dynamics in live Dictyostelium cells.	ACCEPT	Summary: GFP-myosin concentrates in the cleavage furrow during cytokinesis in live cells. Reason: Direct live-cell evidence of myosin II furrow localization during division. Core localization. Supporting Evidence: PMID:8552657 GFP-myosin is concentrated in the cleavage furrow during cytokinesis and in the
GO:0097204 phagocytic cup base	IDA PMID:12952073 Differential localization of the Dictyostelium kinase DPAKa ...	KEEP AS NON CORE	Summary: Myosin II localizes to the base of phagocytic cups and the rear of locomoting cells. Reason: A genuine localization reflecting cortical myosin II during phagocytosis; peripheral to the core cytokinesis/migration functions. Supporting Evidence: PMID:12952073 similar to that of myosin II at the rear end of locomoting cells and at the base
GO:0045179 apical cortex	IDA PMID:22902739 α-catenin and IQGAP regulate myosin localization to control ...	KEEP AS NON CORE	Summary: In tip epithelial cells that surround the stalk, myosin II localizes to the apical cortex to drive epithelial-tube constriction. Reason: A specialized morphogenetic localization during multicellular development; genuine but non-core relative to the motor function. Supporting Evidence: PMID:22902739 myosin II localizes apically in tip epithelial cells that surround the stalk
GO:0030899 calcium-dependent ATPase activity	IDA PMID:7806571 Targeted disruption of the Dictyostelium RMLC gene produces ...	UNDECIDED	Summary: Annotation to a calcium-dependent ATPase activity, cited to a study of the regulatory myosin light chain (RMLC/mlcR) gene disruption. The available abstract does not describe a Ca2+-dependent ATPase measurement for the heavy chain. Reason: Ca2+-ATPase is a non-physiological in vitro myosin assay, and the cited abstract (about RMLC disruption) does not document it. Unable to verify the basis of this specific molecular-function annotation from available text.
GO:0048870 cell motility	IMP PMID:15259052 Keratocyte-like locomotion in amiB-null Dictyostelium cells.	KEEP AS NON CORE	Summary: Myosin II shapes amoeboid locomotion, though keratocyte-like unidirectional movement can occur without it. Reason: Myosin II is dispensable for some modes of unidirectional movement but maintains cell shape during motility; it modulates rather than powers locomotion. Supporting Evidence: PMID:15259052 myosin II is dispensable for the unidirectional movement, though it likely
GO:0048870 cell motility	IGI PMID:15259052 Keratocyte-like locomotion in amiB-null Dictyostelium cells.	KEEP AS NON CORE	Summary: Genetic-interaction evidence (amiB/myosin double knockout) for a modulatory role of myosin II in amoeboid locomotion and shape maintenance. Reason: Consistent with the IMP annotation from the same study; myosin II supports the characteristic migrating cell shape but is not strictly required for movement. Supporting Evidence: PMID:15259052 functions in the maintenance of the characteristic half-moon shape
GO:0060328 cytoplasmic actin-based contraction involved in forward cell motility	IMP PMID:18388319 Actin-based propulsive forces and myosin-II-based contractil...	ACCEPT	Summary: Myosin II motor activity produces the actomyosin contractile forces that propel and retract the cell during forward migration. Reason: Direct evidence that accumulated myosin II generates contractile retraction forces coordinated with actin-based propulsion; a central migratory role. Supporting Evidence: PMID:18388319 the source of the retraction force is the motor activity of accumulated myosin
GO:0032060 bleb assembly	IMP PMID:26317626 Microtubule-Mediated Inositol Lipid Signaling Plays Critical...	KEEP AS NON CORE	Summary: Blebbing (a myosin II-dependent, cortical-contraction-driven protrusion mode) is regulated by microtubule/inositol-lipid signaling. Reason: Bleb formation requires myosin II-driven cortical contraction; this study addresses upstream regulation of blebbing. Genuine but non-core role. Supporting Evidence: PMID:16624291 cortical contraction involving myosin-II
GO:0005515 protein binding	IPI PMID:30559246 Contractility kits promote assembly of the mechanoresponsive...	KEEP AS NON CORE	Summary: Protein binding reflecting myosin II's incorporation into mechanoresponsive contractility kits. Reason: A real assembly interaction, but the bare protein binding term is uninformative; retained as non-core with the contractility-kit context noted. Supporting Evidence: PMID:30559246 Cellular contractility is governed by a control system of proteins that
GO:0000146 microfilament motor activity	IDA PMID:16982629 Functional characterization of the N-terminal region of myos...	ACCEPT	Summary: Functional dissection of the myosin-2 N-terminal region shows its motor/motile activity and actin/ADP affinities, confirming actin-based motor function. Reason: Truncations altering motile activity and actin affinity directly demonstrate the actin-based motor activity of Dictyostelium myosin-2. Core function. Supporting Evidence: PMID:16982629 changes of similar extent in the affinity for ADP and
GO:0000146 microfilament motor activity	IDA PMID:19955408 Unique charge distribution in surface loops confers high vel...	ACCEPT	Summary: Charge manipulation of surface loops in Dictyostelium myosin II (class II) alters its sliding velocity, an assay of actin-based motor activity. Reason: The study directly manipulates and measures the motility of Dictyostelium myosin II, supporting its microfilament motor activity. Supporting Evidence: PMID:19955408 charge contents in loops 2 and 3 of Dictyostelium
GO:0003774 cytoskeletal motor activity	IDA PMID:15910751 Evidence against essential roles for subdomain 1 of actin in...	ACCEPT	Summary: Actomyosin sliding assays using the Dictyostelium myosin II motor domain demonstrate cytoskeletal (actin-based) motor activity. Reason: MgATPase and in vitro sliding measurements with the Dictyostelium myosin II motor domain confirm cytoskeletal motor activity. Supporting Evidence: PMID:15910751 the motor domain of Dictyostelium myosin II
GO:0005515 protein binding	IPI PMID:11106661 WD repeat domains target dictyostelium myosin heavy chain ki...	KEEP AS NON CORE	Summary: Protein binding reflecting the direct interaction of myosin heavy chain kinase WD-repeat domains with myosin II filaments (myosin as the substrate). Reason: A specific, informative interaction (MHCK targeting to myosin filaments), but the bare protein binding term understates it; retained as non-core with the partner noted. Supporting Evidence: PMID:11106661 the mechanism of targeting involves direct binding of the WD repeat domains to the
GO:0005515 protein binding	IPI PMID:18504297 Linking Ras to myosin function: RasGEF Q, a Dictyostelium ex...	KEEP AS NON CORE	Summary: Protein binding within the RasB/RasGEF Q/MHCK A signaling module that regulates myosin II assembly. Reason: Reflects a regulatory interaction affecting myosin II function; the generic term is uninformative and the interaction is upstream regulatory rather than a core myosin activity. Supporting Evidence: PMID:18504297 increased levels of unphosphorylated myosin II, resulting in myosin II
GO:0005524 ATP binding	IDA PMID:16982629 Functional characterization of the N-terminal region of myos...	ACCEPT	Summary: Nucleotide (ADP/ATP) affinity measurements on Dictyostelium myosin-2 constructs confirm nucleotide binding by the motor domain. Reason: The motor domain binds and hydrolyzes ATP; nucleotide-affinity changes were directly measured. Core function. Supporting Evidence: PMID:16982629 changes of similar extent in the affinity for ADP and
GO:0005524 ATP binding	IDA PMID:4278009 Biochemical and structural studies of actomyosin-like protei...	ACCEPT	Summary: Biochemical characterization of isolated Dictyostelium myosin, including its ATPase activity. Reason: The isolated myosin binds and hydrolyzes ATP; ATP binding is a core property of the motor domain. Supporting Evidence: PMID:4278009 Isolation and characterization of myosin from amoebae of Dictyostelium
GO:0005826 actomyosin contractile ring	IDA PMID:9238018 A novel role for clathrin in cytokinesis.	ACCEPT	Summary: Myosin II assembles into the functional contractile ring during cytokinesis (shown by its failure to do so in clathrin-minus cells). Reason: Assembly of myosin II into the contractile ring is central to cytokinesis; a core localization/activity. Supporting Evidence: PMID:9238018 failed to assemble myosin II into a functional contractile ring
GO:0005856 cytoskeleton	IDA PMID:2578450 Quantitative immunochemical studies of myosin in Dictyosteli...	ACCEPT	Summary: A large fraction of cellular myosin II is associated with the Triton-insoluble cytoskeleton/cortical actin matrix. Reason: Quantitative immunochemistry shows myosin II partitions with the cytoskeleton; correct though general relative to cell cortex. Supporting Evidence: PMID:2578450 contain nearly half of the cell's myosin
GO:0005938 cell cortex	IDA PMID:16461463 Dictyostelium myosin II mechanochemistry promotes active beh...	ACCEPT	Summary: Myosin II is highly enriched in and mechanically active at the cell cortex. Reason: Cortical enrichment and mechanochemical activity of myosin II is a core localization underpinning cortical tension. Core. Supporting Evidence: PMID:16461463 Highly enriched in the cell cortex, actin, myosin II
GO:0030554 adenyl nucleotide binding	IDA PMID:14620745 Probing nucleotide dissociation from myosin in vitro using m...	ACCEPT	Summary: Nucleotide-dissociation kinetics measured on the Dictyostelium cytoplasmic myosin II motor domain confirm adenine-nucleotide binding. Reason: The motor domain binds adenine nucleotides (ATP/ADP); a general parent of ATP binding and correct. Supporting Evidence: PMID:14620745 Dictyostelium cytoplasmic myosin II
GO:0030864 cortical actin cytoskeleton	IDA PMID:3243031 Electron microscopic localization of myosin II and ABP-120 i...	ACCEPT	Summary: Immuno-EM localizes myosin II to the cortical actin matrix in lateral filament arrays. Reason: Myosin II operates within the cortical actin cytoskeleton; a core localization for its contractile function. Supporting Evidence: PMID:3243031 myosin II and ABP-120 in the cortical actin
GO:0032982 myosin filament	IDA PMID:4278009 Biochemical and structural studies of actomyosin-like protei...	ACCEPT	Summary: Isolated Dictyostelium myosin forms filaments, the active force-generating assembly. Reason: The heavy chain self-assembles into (thick) myosin filaments; core structural localization. Supporting Evidence: PMID:4278009 Isolation and characterization of myosin from amoebae of Dictyostelium
GO:0042641 actomyosin	IDA PMID:4278009 Biochemical and structural studies of actomyosin-like protei...	ACCEPT	Summary: The classic study characterized actomyosin-like proteins from Dictyostelium, of which myosin II is a component. Reason: Myosin II is a defining component of actomyosin; correct localization. Supporting Evidence: PMID:4278009 Isolation and characterization of myosin from amoebae of Dictyostelium
GO:0042802 identical protein binding	IPI PMID:2745547 Intermolecular versus intramolecular interactions of Dictyos...	ACCEPT	Summary: Rotary-shadowing shows myosin molecules self-associate into parallel dimers and tetramers via tail-tail interactions during filament assembly. Reason: Homotypic self-assembly of myosin heavy chains through their tails is a core activity that builds bipolar thick filaments; captured by identical protein binding. Supporting Evidence: PMID:2745547 Parallel dimers form tetramers by way of antiparallel interactions in their tail
GO:0051015 actin filament binding	IDA PMID:16982629 Functional characterization of the N-terminal region of myos...	ACCEPT	Summary: Direct measurement of filamentous-actin affinity for Dictyostelium myosin-2 constructs. Reason: The myosin II motor domain binds F-actin; actin affinity was directly measured. Core function. Supporting Evidence: PMID:16982629 changes of similar extent in the affinity for ADP and
GO:0051015 actin filament binding	IDA PMID:18067324 Kinetic characterization of the function of myosin loop 4 in...	ACCEPT	Summary: Kinetic analysis identifies myosin loop 4 as an actin-binding region that stabilizes the actomyosin complex. Reason: Direct evidence that the Dictyostelium myosin II motor domain binds actin filaments. Core function. Supporting Evidence: PMID:18067324 loop 4 is a functional actin-binding region that stabilizes actomyosin
GO:0071889 14-3-3 protein binding	IPI PMID:20951045 14-3-3 coordinates microtubules, Rac, and myosin II to contr...	KEEP AS NON CORE	Summary: 14-3-3 associates directly with myosin II heavy chain to promote bipolar thick filament remodeling. Reason: A specific, verified interaction that regulates myosin II filament dynamics during cytokinesis; a genuine binding activity but regulatory/non-core relative to the motor function. Supporting Evidence: PMID:20951045 14-3-3 interacts directly with myosin II heavy chain to promote bipolar thick
GO:1903013 response to differentiation-inducing factor 1	HDA PMID:25518940 The Dictyostelium prestalk inducer differentiation-inducing ...	KEEP AS NON CORE	Summary: Phosphoproteomics after DIF-1 treatment detected changes in actomyosin-cytoskeletal signaling components, including myosin. Reason: Reflects DIF-1-induced phosphorylation changes in cytoskeletal signaling; a developmental-signaling response rather than a core molecular function. Supporting Evidence: PMID:25518940 components of the actinomyosin cytoskeletal signaling networks
GO:1990753 equatorial cell cortex	IDA PMID:19515202 PTEN is a mechanosensing signal transducer for myosin II loc...	ACCEPT	Summary: Myosin II localizes to the equatorial cortex/furrow region of dividing cells. Reason: Equatorial cortex enrichment underlies contractile-ring formation during cytokinesis; core localization. Supporting Evidence: PMID:19515202 region of dividing cells
GO:0051591 response to cAMP	IDA PMID:2543508 Changes in the association of actin-binding proteins with th...	KEEP AS NON CORE	Summary: Cytoskeletal myosin content changes following chemotactic cAMP stimulation of Dictyostelium amoebae. Reason: Myosin II redistributes in response to cAMP signaling during chemotaxis; a signaling-linked behavior rather than a core molecular function. Supporting Evidence: PMID:2543508 Changes in the content of total cytoskeletal protein and cytoskeletal myosin were
GO:0042542 response to hydrogen peroxide	IDA PMID:21988699 Structural and functional impact of site-directed methionine...	KEEP AS NON CORE	Summary: Site-directed and peroxide-induced methionine oxidation of Dictyostelium myosin II decreases actin-activated ATPase activity. Reason: Documents oxidative sensitivity of myosin II function rather than a physiological signaling role; retained as non-core. Supporting Evidence: PMID:21988699 peroxide treatment decreased actin-activated myosin ATPase activity
GO:0006971 hypotonic response	IMP PMID:19843280 Roles of an unconventional protein kinase and myosin II in a...	KEEP AS NON CORE	Summary: The cortical myosin II cytoskeleton contributes to contractile-vacuole function required for osmotic homeostasis. Reason: Myosin II supports the periodic contractions of the contractile vacuole that protect against osmotic (hypotonic) stress; a downstream physiological role. Supporting Evidence: PMID:19843280 myosin II null cells also results in enlarged CVs with impaired dynamics
GO:0033275 actin-myosin filament sliding	IDA PMID:19955408 Unique charge distribution in surface loops confers high vel...	ACCEPT	Summary: In vitro motility of Dictyostelium myosin II, measured as actin-myosin sliding velocity, is altered by surface-loop charge changes. Reason: Direct measurement of actin-myosin filament sliding by Dictyostelium myosin II; a core mechanochemical activity. Supporting Evidence: PMID:19955408 charge contents in loops 2 and 3 of Dictyostelium
GO:0032060 bleb assembly	IMP PMID:16926192 Dissection of amoeboid movement into two mechanically distin...	KEEP AS NON CORE	Summary: Bleb formation at the leading edge during amoeboid movement requires myosin II activity. Reason: Myosin II-driven cortical contraction is required for blebbing, a distinct protrusion mode contributing to motility; genuine but non-core. Supporting Evidence: PMID:16926192 Their formation requires the activity of myosin II
GO:0031034 myosin filament assembly	IDA PMID:4278009 Biochemical and structural studies of actomyosin-like protei...	ACCEPT	Summary: Isolated Dictyostelium myosin self-assembles into filaments, a biochemically characterized process. Reason: Myosin heavy chains self-assemble into bipolar thick filaments; myosin filament assembly is a core structural activity. Supporting Evidence: PMID:15492777 forms bipolar thick filament (BTF) structures
GO:0033275 actin-myosin filament sliding	IDA PMID:16901894 A point mutation in the SH1 helix alters elasticity and ther...	ACCEPT	Summary: A point mutation in the SH1 helix of Dictyostelium myosin II impairs motile activity, assayed as actin-myosin sliding. Reason: The single-molecule and in vitro motility measurements directly assay actin-myosin sliding by Dictyostelium myosin II. Core mechanochemical activity. Supporting Evidence: PMID:16901894 significant impairment in motile activities
GO:0030866 cortical actin cytoskeleton organization	IDA PMID:16461463 Dictyostelium myosin II mechanochemistry promotes active beh...	KEEP AS NON CORE	Summary: Myosin II mechanochemistry, antagonized by dynacortin crosslinking, shapes the dynamic behavior of the cortical actin cytoskeleton. Reason: Myosin II contributes to cortical cytoskeleton dynamics via its contractile activity; a downstream organizational role rather than the core motor function. Supporting Evidence: PMID:16461463 myosin II and dynacortin antagonistically regulate other active processes in the
GO:0008104 intracellular protein localization	IMP PMID:16339076 Contractile ring-independent localization of DdINCENP, a pro...	KEEP AS NON CORE	Summary: Myosin II modulates the cleavage-furrow localization of the chromosomal passenger protein DdINCENP. Reason: Myosin II influences localization of other furrow proteins as part of its cytokinesis role; a downstream effect rather than a core molecular function. Supporting Evidence: PMID:16339076 the localization of DdINCENP at the cleavage furrow is
GO:0032060 bleb assembly	IMP PMID:16624291 Blebbing of Dictyostelium cells in response to chemoattracta...	KEEP AS NON CORE	Summary: Chemoattractant-induced blebbing is driven by hydrostatic pressure from myosin II cortical contraction; myosin-null cells fail to bleb. Reason: Myosin II is strictly required for bleb formation (cells lacking myosin II completely fail to bleb), but blebbing is a specialized motility behavior secondary to the core motor function. Supporting Evidence: PMID:16624291 completely fail to bleb

Gene Description

Existing Annotations Review

Core Functions

Self-assembly into bipolar thick filaments. Two heavy chains dimerize through their coiled-coil tails and self-associate tail-to-tail into bipolar thick filaments, the functional force-generating assembly; this assembly is reversibly regulated by heavy chain phosphorylation.

ATP-dependent actin filament binding. The motor domain binds filamentous actin in a nucleotide-dependent manner, an integral step of the mechanochemical cycle that couples ATP hydrolysis to actin-myosin filament sliding.

References

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