pstC

UniProt ID: A0A0H2MMT5
Organism: Variovorax paradoxus
Review Status: COMPLETE
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Gene Description

Phosphate transport system permease protein PstC (VPARA_10470, A0A0H2MMT5) is a 359-amino-acid six-pass inner-membrane subunit of the high-affinity PstSCAB ABC orthophosphate importer in Variovorax paradoxus strain TBEA6, encoded on genomic contig JZWI01000005 (EMBL KLN58035.1) between pstS (VPARA_10480) and pstA (VPARA_10460) within the phoR1-phoB1-phoU-pstB-pstA-pstC-pstS-ppx cluster (VPARA_10420-VPARA_10490). PstC contains six transmembrane alpha-helices (residues 65-88, 108-139, 151-175, 195-221, 266-288, and 325-348) forming a MetI-like type-1 ABC transmembrane domain (PROSITE PS50928, Pfam PF00528, CDD cd06261, InterPro IPR011864, NCBIfam TIGR02138, PANTHER PTHR30425:SF1) and conserves the essential Arg276 and Glu280 residues (within 274-LGRALGETM-282) required for phosphate translocation. PstC heterodimerizes with PstA in the plasma membrane to form the transmembrane orthophosphate translocation pathway gated by periplasmic PstS and energized by the cytoplasmic PstB ATPase dimer.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0005315 phosphate transmembrane transporter activity
IEA
GO_REF:0000002 		MARK AS OVER ANNOTATED
Summary: PstC is one of two heterodimeric transmembrane permease subunits of the PstSCAB complex; it contributes to holocomplex phosphate transmembrane transporter activity rather than independently enabling it.
Reason: Following the curation convention for ECOLI/pstC (UniProtKB:P0AGH8), PstC is an essential transmembrane subunit of the PstSCAB importer (PMID:2646285, PMID:24563032), but GO:0005315 is enabled by the assembled PstSCAB complex rather than by PstC in isolation. PstC's contribution to the holocomplex ATPase-coupled phosphate ion transmembrane transporter activity (GO:0015415) is captured via contributes_to_molecular_function in core_functions.
Supporting Evidence:
file:VARPD/pstC/pstC-uniprot.txt
CC -!- FUNCTION: Part of the binding protein-dependent transport system for CC phosphate; probably responsible for the translocation of the substrate CC across the membrane. {ECO:0000256|RuleBase:RU363054}.
GO:0005886 plasma membrane
IEA
GO_REF:0000044 		ACCEPT
Summary: Core subcellular localization of this six-pass inner-membrane ABC permease subunit.
Reason: PstC contains six transmembrane helices (residues 65-88, 108-139, 151-175, 195-221, 266-288, and 325-348; RuleBase RU363054, PROSITE PS50928) embedded in the bacterial inner (plasma) membrane (PMID:24563032; matching ECOLI/pstC).
Supporting Evidence:
file:VARPD/pstC/pstC-uniprot.txt
CC -!- SUBCELLULAR LOCATION: Cell inner membrane CC {ECO:0000256|RuleBase:RU363054}; Multi-pass membrane protein CC {ECO:0000256|RuleBase:RU363054}.
GO:0006817 phosphate ion transport
IEA
GO_REF:0000002 		MODIFY
Summary: Correct but general biological process; refine to GO:0035435 (phosphate ion transmembrane transport).
Reason: PstC forms half of the transmembrane pore of the PstSCAB ABC importer and directly mediates transmembrane translocation of orthophosphate across the inner membrane (PMID:2646285, PMID:24563032); refine generic GO:0006817 to its specific child GO:0035435 (phosphate ion transmembrane transport).
Supporting Evidence:
file:VARPD/pstC/pstC-uniprot.txt
CC -!- FUNCTION: Part of the binding protein-dependent transport system for CC phosphate; probably responsible for the translocation of the substrate CC across the membrane. {ECO:0000256|RuleBase:RU363054}.
PMID:2646285
The amino acid substitutions resulting from the pstC gene mutations, Arg-237----Gln, Glu-240----Gln, or a combination of both, caused the loss of phosphate transport through the Pst system
GO:0016020 membrane
IEA
GO_REF:0000120 		TOO GENERAL
Summary: True but uninformative parent cellular component already entailed by the accepted specific child term GO:0005886 (plasma membrane).
Reason: GO:0016020 (membrane) is a broad ancestor term that adds no specificity beyond GO:0005886 (plasma membrane) already accepted in this review.
Supporting Evidence:
file:VARPD/pstC/pstC-uniprot.txt
CC -!- SUBCELLULAR LOCATION: Cell inner membrane CC {ECO:0000256|RuleBase:RU363054}; Multi-pass membrane protein CC {ECO:0000256|RuleBase:RU363054}.
GO:0043190 ATP-binding cassette (ABC) transporter complex
IEA
GO_REF:0000104 		MODIFY
Summary: Correct but general cellular component; refine to GO:0055052 (ATP-binding cassette (ABC) transporter complex, substrate-binding subunit-containing).
Reason: PstC is a transmembrane permease subunit of the binding-protein-dependent PstSCAB ABC importer complex (PMID:3881386, PMID:24563032); refine GO:0043190 to its specific child GO:0055052, matching ECOLI/pstC.
Supporting Evidence:
file:VARPD/pstC/pstC-uniprot.txt
CC -!- FUNCTION: Part of the binding protein-dependent transport system for CC phosphate; probably responsible for the translocation of the substrate CC across the membrane. {ECO:0000256|RuleBase:RU363054}.
PMID:24563032
PstS is the periplasmic P i -binding protein, PstC and PstA are integral membrane proteins that form the pore through which P i passes, and PstB is the dimeric, cytoplasmic ATPase.
GO:0055085 transmembrane transport
IEA
GO_REF:0000002 		MODIFY
Summary: Correct but general biological process; refine to GO:0035435 (phosphate ion transmembrane transport).
Reason: Generic GO:0055085 (transmembrane transport) from the MetI-like superfamily (InterPro IPR000515) is refined to the specific descendant GO:0035435 (phosphate ion transmembrane transport) supported by PstC family membership (InterPro IPR011864, NCBIfam TIGR02138, PANTHER PTHR30425:SF1) and operon context.
Supporting Evidence:
file:VARPD/pstC/pstC-uniprot.txt
DR NCBIfam; TIGR02138; phosphate_pstC; 1. DR PANTHER; PTHR30425; PHOSPHATE TRANSPORT SYSTEM PERMEASE PROTEIN PST; 1. DR PANTHER; PTHR30425:SF1; PHOSPHATE TRANSPORT SYSTEM PERMEASE PROTEIN PSTC; 1.
GO:0035435 phosphate ion transmembrane transport
IC
file:VARPD/pstC/pstC-uniprot.txt 		NEW
Summary: Core biological process; PstC partners with PstA to form the inner-membrane orthophosphate translocation pore of the PstSCAB ABC importer.
Reason: Inferred by curator (IC) from PstC orthology (InterPro IPR011864, NCBIfam TIGR02138, PANTHER PTHR30425:SF1), conservation of the catalytic/coupling Arg276 and Glu280 residues in 274-LGRALGETM-282 (PMID:2646285), and co-organization with pstS-pstA-pstB-phoU (VPARA_10440-VPARA_10480; PMID:3881386, PMID:24563032).
Supporting Evidence:
file:VARPD/pstC/pstC-uniprot.txt
CC -!- FUNCTION: Part of the binding protein-dependent transport system for CC phosphate; probably responsible for the translocation of the substrate CC across the membrane. {ECO:0000256|RuleBase:RU363054}.
PMID:2646285
The amino acid substitutions resulting from the pstC gene mutations, Arg-237----Gln, Glu-240----Gln, or a combination of both, caused the loss of phosphate transport through the Pst system
GO:0055052 ATP-binding cassette (ABC) transporter complex, substrate-binding subunit-containing
IC
file:VARPD/pstC/pstC-uniprot.txt 		NEW
Summary: PstC is an integral transmembrane permease subunit of the substrate-binding-protein-dependent PstSCAB ABC importer complex.
Reason: Inferred by curator (IC) from RuleBase RU363054 and co-localization in the VPARA_10450-VPARA_10480 (pstB-pstA-pstC-pstS) operon (PMID:3881386, PMID:24563032; matching ECOLI/pstC).
Supporting Evidence:
file:VARPD/pstC/pstC-uniprot.txt
CC -!- FUNCTION: Part of the binding protein-dependent transport system for CC phosphate; probably responsible for the translocation of the substrate CC across the membrane. {ECO:0000256|RuleBase:RU363054}.
PMID:24563032
PstS is the periplasmic P i -binding protein, PstC and PstA are integral membrane proteins that form the pore through which P i passes, and PstB is the dimeric, cytoplasmic ATPase.

Core Functions

Partners with PstA in the plasma membrane to form the transmembrane permease channel of the PstSCAB ABC importer that contributes phosphate transmembrane transporter activity during ATP-dependent orthophosphate import.

Directly Involved In:
phosphate ion transmembrane transport
Cellular Locations:
plasma membrane
In Complex:
ATP-binding cassette (ABC) transporter complex, substrate-binding subunit-containing
Supporting Evidence:
  • file:VARPD/pstC/pstC-uniprot.txt
    CC -!- FUNCTION: Part of the binding protein-dependent transport system for CC phosphate; probably responsible for the translocation of the substrate CC across the membrane. {ECO:0000256|RuleBase:RU363054}.
  • PMID:2646285
    The amino acid substitutions resulting from the pstC gene mutations, Arg-237----Gln, Glu-240----Gln, or a combination of both, caused the loss of phosphate transport through the Pst system
  • PMID:24563032
    PstS is the periplasmic P i -binding protein, PstC and PstA are integral membrane proteins that form the pore through which P i passes, and PstB is the dimeric, cytoplasmic ATPase.

References

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Suggested Questions for Experts

Q: What is the functional role of the 51-residue N-terminal disordered polar extension (residues 1-51) in Variovorax paradoxus PstC (VPARA_10470) in stabilizing the PstCA-PstB-PhoU signaling complex at the inner membrane?

Suggested experts: McCleary WR

Suggested Experiments

Experiment: Construct site-directed Arg276Gln and Glu280Gln substitutions in VPARA_10470 (pstC) in Variovorax paradoxus TBEA6 and assay high-affinity [32P]orthophosphate uptake and PhoB1-regulated alkaline phosphatase repression.

Hypothesis: Substitutions at Arg276 or Glu280 abolish PstSCAB-mediated orthophosphate transport while preserving PhoU-dependent repression of PhoR1-PhoB1 under phosphate-replete conditions, mirroring E. coli pstC mutants (PMID:2646285).

📚 Additional Documentation

Notes

(pstC-notes.md)

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