MotC (PA1460) is the A subunit of the MotCD flagellar stator of Pseudomonas aeruginosa, a MotA-like polytopic inner-membrane protein of the MotA/TolQ/ExbB family that, with MotD (PA1461), forms an ion-conducting stator unit generating torque at the rotor of the single polar flagellum. MotCD and the second stator, MotAB (PA4954-PA4953), are redundant for swimming, and loss of both MotA homologues abolishes motility. MotCD is the stator required for swarming on firmer (0.5% agar or more) surfaces and for efficient translocation through semisolid agar, which makes it the main surface-motility stator; high c-di-GMP reduces MotCD function, in part by MotAB displacing it from the motor.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005886 plasma membrane | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping; the UniProt location line is ARBA-predicted. Reason: MotC has three predicted transmembrane helices plus the MotA_N region and belongs to the MotA-like family; stator units are inner-membrane complexes. The TM prediction and the stator role agree with the location. Supporting Evidence: file:PSEAE/motC/motC-uniprot.txt TRANSMEM 29..49 PMID:15629949 the stator (the stationary component of the motor within which the rotor turns), which is composed of two integral membrane proteins, MotA and MotB |
| GO:0006935 chemotaxis | IEA GO_REF:0000002 | MARK AS OVER ANNOTATED | Summary: InterPro2GO mapping from the MotA-like family signature. Reason: The stator is the output of chemotaxis signalling, not part of it. Doyle et al. tested the PA1460-PA1461 mutants (their "motAB") directly and found normal chemotaxis to arginine, so the motility-plate defect is not a chemotaxis defect. Supporting Evidence: PMID:15375113 Therefore, the radial expansion defect observed for motAB strains in semisolid motility agar cannot be attributed to polar effects that disturb chemotaxis. |
| GO:0016020 membrane | IEA GO_REF:0000044 | MODIFY | Summary: UniProt subcellular-location mapping to a generic membrane. Reason: Correct but general; the specific location is plasma membrane, which the gene already carries (IEA, accepted above). Proposed replacements: plasma membrane Supporting Evidence: file:PSEAE/motC/motC-uniprot.txt TRANSMEM 29..49 |
| GO:0071973 bacterial-type flagellum-dependent cell motility | IMP PMID:15375113 The complex flagellar torque generator of Pseudomonas aerugi... | MODIFY | Summary: Doyle et al. 2004 (who call PA1460-PA1461 "motAB", the reverse of current usage): PA1460 mutants are severely impaired in semisolid agar and on swarm plates, and loss of both MotA homologues abolishes motility. Reason: Correct but general. Both specific descendants are supported for MotC and the review asserts both. Swarming (GO:0071978) is the distinctive role (single-mutant defect, accepted below). Swimming (GO:0071977) is shown by the double stator mutant, which does not swim, and by partial restoration of swimming with motCD alone. Listing both captures what the general term says without losing the swarming specificity. Proposed replacements: bacterial-type flagellum-dependent swimming motility bacterial-type flagellum-dependent swarming motility Supporting Evidence: PMID:15375113 Mutation of both genes encoding the MotA homologs or MotB homologs was sufficient to abolish motility. PMID:15375113 MotA, MotB, and MotY are necessary to power movement on surfaces. PMID:15629949 The pMMB66EH- motCD plasmid also partially complemented the swimming defect of the Ξ motAB Ξ motCD mutant |
| GO:0071978 bacterial-type flagellum-dependent swarming motility | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from PTN001252377 (MotA clade), seeded by the PseudoCAP IMP swarming rows on MotC (PA1460, this protein) and MotA (PA4954). Reason: True for MotC: the motCD single mutant fails to swarm on 0.5% agar or firmer, and motCD alone restores swarming to the double stator mutant. The self-reference in WITH/FROM is the expected mark of a seed and of experimental grounding on the target itself. The row is accepted for this gene, but the node term is too specific for the 29-leaf clade (see the GO_CENTRAL defect, recorded here once for the node and cross-referenced from motA). Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH CONTEXT OR TISSUE MISMATCH Sources checked: PANTHER:PTN001252377 Β· PTN001252377 SOURCE WEAK OR INFERRED PAINT leaf GAF (cached) lists 29 GO:0071978 leaves in 19 taxa. Flagellar rotation, not surface swarming, is the shared role: the clade's one experimentally characterised leaf, E. coli MotA (UniProtKB:P09348), has GO:0071973 by IMP, GO:0015252 proton channel activity and GO:0120101 stator complex by IPI, and in QuickGO (checked 2026-11-06) every GO:0071978 row on the 24 non-PAO1 leaves is IBA or IEA. UniProtKB:G3XD73 Β· motC (self) SUPPORTS SOURCE BUT NOT TARGET Sound seed for P. aeruginosa (single-mutant swarming defect), but a surface-motility phenotype of one stator of a two-stator organism does not support a clade-wide swarming claim. UniProtKB:Q9HUL1 Β· motA (PA4954) SOURCE WEAK OR INFERRED Weak co-seed; the motAB single mutant swarms like wild type or better (see genes/PSEAE/motA). Supporting Evidence: PMID:15629949 In contrast, the Ξ motCD mutant can swarm to a degree comparable to that of the WT in a relatively low agar concentration (0.45%), but not at higher concentrations tested (above or equal to 0.5%). |
| GO:0071978 bacterial-type flagellum-dependent swarming motility | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO mapping from the MotA-like family signature. Reason: Same claim as the accepted IMP and IBA rows; true for MotC, which is the stator P. aeruginosa needs for swarming. (A family-wide mapping is over-specific in general, as for the IBD.) Supporting Evidence: PMID:15629949 In contrast, the Ξ motCD mutant can swarm to a degree comparable to that of the WT in a relatively low agar concentration (0.45%), but not at higher concentrations tested (above or equal to 0.5%). |
| GO:0071978 bacterial-type flagellum-dependent swarming motility | IMP PMID:15629949 Evidence for two flagellar stators and their role in the mot... | ACCEPT | Summary: PseudoCAP IMP from Toutain et al. 2005 (PA14): the motCD deletion does not swarm on 0.5% agar or firmer, and plasmid motCD restores swarming to the double stator mutant. Reason: Sound seed. A single-mutant defect with complementation, for a stator subunit that does part of the work of flagellar rotation, is direct evidence of participation. Doyle et al. found the same for PA1460 mutants (which they call motA) in PAK and PAO1. Supporting Evidence: PMID:15629949 In contrast, the Ξ motCD mutant can swarm to a degree comparable to that of the WT in a relatively low agar concentration (0.45%), but not at higher concentrations tested (above or equal to 0.5%). PMID:15629949 The Ξ motAB Ξ motCD /pMMB66EH- motCD strain swarmed (31.8 Β± 2.5 mm) to a degree comparable to that of the WT (42.2 Β± 4.2 mm) on 0.5% agar PMID:15375113 MotA, MotB, and MotY are necessary to power movement on surfaces. |
| GO:0120101 bacterial-type flagellum stator complex | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from PTN001252377, seeded by E. coli MotA (P09348). Reason: Core location. MotCD is described experimentally as one of the two stator complexes of the polar flagellum, functionally interchangeable with MotAB for swimming. Supporting Evidence: PMID:25349157 P. aeruginosa encodes two stator complexes, MotAB and MotCD, that participate in the function of its single polar flagellum. PMID:15629949 The second putative stator was designated MotCD (PA1460-1461) based on its lower degree of sequence similarity to MotAB. |
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Download this section (compressed HTML)Q: What property of MotCD (ion conductance, torque at high load, or stator retention under load) makes it, and not MotAB, the stator needed for swarming on firmer surfaces?
Experiment: Compare single-motor torque-speed curves and stator dwell times of motAB-only and motCD-only strains under increasing viscous load, to test whether MotCD supports higher-load rotation on surfaces.
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