KtrA (also called TrkA; SAUSA300_0988) is the cytoplasmic gating component of the Staphylococcus aureus USA300 Ktr potassium uptake system. Its RCK domains regulate the membrane transport machinery, and the RCK_C domain directly binds cyclic di-AMP. This nucleotide-dependent gating helps tune potassium uptake to ionic and osmotic conditions. KtrA is a regulator of the conducting subunit rather than the membrane pore itself.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0006813 potassium ion transport | IEA GO_REF:0000002 | MODIFY | Summary: The directly demonstrated role is regulation of potassium transport. Reason: The protein directly interacts with and regulates the conducting component. This is a role refinement to potassium-transport regulation, rather than an assignment of pore-mediated ion translocation to the soluble regulator. Proposed replacements: regulation of potassium ion transport Supporting Evidence: PMID:23671116 Using an affinity pull-down assay we identified the potassium transporter-gating component KtrA as a c-di-AMP receptor protein |
| GO:0008324 monoatomic cation transmembrane transporter activity | IEA GO_REF:0000002 | MODIFY | Summary: The protein regulates a transporter rather than independently conducting cations. Reason: The InterPro mapping is too broad in molecular role: this soluble RCK protein is the gating subunit. The existing potassium channel regulator annotation represents its direct activity. GO:0015459 denotes binding to and modulation of a potassium channel. PMID:23815639 directly characterizes the USA300 LAC Ktr system as one regulator and two ion-conducting channels, supporting this specific regulator term rather than broadening solely because the system also transports potassium. Proposed replacements: potassium channel regulator activity Supporting Evidence: PMID:23671116 Using an affinity pull-down assay we identified the potassium transporter-gating component KtrA as a c-di-AMP receptor protein PMID:23815639 one regulatory protein and two ion-conducting channels required for K+-limited growth of S. aureus in alkaline conditions. |
| GO:0015459 potassium channel regulator activity | IEA GO_REF:0000104 | ACCEPT | Summary: Potassium channel regulation is the direct role of KtrA. Reason: The specific RCK regulator inference agrees with direct identification of KtrA as the potassium transporter-gating component and c-di-AMP receptor. GO:0015459 denotes binding to and modulation of a potassium channel. PMID:23815639 directly characterizes the USA300 LAC Ktr system as one regulator and two ion-conducting channels, supporting this specific regulator term rather than broadening solely because the system also transports potassium. Supporting Evidence: PMID:23671116 Using an affinity pull-down assay we identified the potassium transporter-gating component KtrA as a c-di-AMP receptor protein PMID:23671116 We defined the c-di-AMP binding activity within KtrA to the RCK_C (regulator of conductance of K(+)) domain. PMID:23815639 one regulatory protein and two ion-conducting channels required for K+-limited growth of S. aureus in alkaline conditions. |
| GO:0043266 regulation of potassium ion transport | IEA GO_REF:0000104 | ACCEPT | Summary: KtrA regulates potassium transport through the Ktr system. Reason: The gating component is an active part of potassium regulation, with direct nucleotide binding providing a regulatory input. Supporting Evidence: PMID:23671116 Using an affinity pull-down assay we identified the potassium transporter-gating component KtrA as a c-di-AMP receptor protein PMID:23671116 We defined the c-di-AMP binding activity within KtrA to the RCK_C (regulator of conductance of K(+)) domain. |
| GO:0098655 monoatomic cation transmembrane transport | IEA GO_REF:0000108 | MODIFY | Summary: The directly demonstrated role is regulation of potassium transport. Reason: The protein directly interacts with and regulates the conducting component. This is a role refinement to potassium-transport regulation, rather than an assignment of pore-mediated ion translocation to the soluble regulator. Proposed replacements: regulation of potassium ion transport Supporting Evidence: PMID:23671116 Using an affinity pull-down assay we identified the potassium transporter-gating component KtrA as a c-di-AMP receptor protein |
| GO:0180001 cyclic-di-AMP binding | IDA PMID:23671116 Systematic identification of conserved bacterial c-di-AMP re... | NEW | Summary: Cyclic di-AMP binding is an experimentally established receptor activity. Reason: Direct affinity-pull-down and binding-domain experiments identify USA300 SAUSA300_0988 as a cyclic di-AMP receptor. The molecular activity is independently demonstrated and is not entailed by potassium-channel regulator activity. Supporting Evidence: PMID:23671116 We defined the c-di-AMP binding activity within KtrA to the RCK_C (regulator of conductance of K(+)) domain. |
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