pstB

UniProt ID: A0A0D0L7E0
Organism: Variovorax paradoxus
Review Status: COMPLETE
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Gene Description

Phosphate import ATP-binding protein PstB (VPARA_10450, A0A0D0L7E0) is the 259-amino-acid cytoplasmic nucleotide-binding ATPase subunit of the high-affinity PstSCAB ABC orthophosphate importer in Variovorax paradoxus strain TBEA6, encoded on genomic contig JZWI01000005 (EMBL KLN58033.1) between pstA (VPARA_10460) and phoU (VPARA_10440) within the phoR1-phoB1-phoU-pstB-pstA-pstC-pstS-ppx cluster (VPARA_10420-VPARA_10490). PstB folds into a P-loop ABC ATPase domain (residues 13-254; PROSITE PS50893, Pfam PF00005, CDD cd03260, InterPro IPR005670, NCBIfam TIGR00972, PANTHER PTHR43423:SF3) preserving the Walker A ATP-binding motif (45-GPSGCGKS-52, including Gly50 and Lys51), the ABC signature motif (156-LSGGQQQRLCIAR-168, PROSITE PS00211), the Walker B catalytic glutamate (Glu181 in 176-VLLLDEPCSALD-187), and the switch histidine (His212). A PstB homodimer associates peripherally with the cytoplasmic face of the inner-membrane PstCA permease to couple ATP hydrolysis to orthophosphate import, and also physically interacts with PhoU to transmit the phosphate-transport signaling state to the PhoR1 sensor kinase.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0000166 nucleotide binding
IEA
GO_REF:0000104 		TOO GENERAL
Summary: True but uninformative parent molecular function already entailed by GO:0005524 (ATP binding).
Reason: GO:0000166 (nucleotide binding) is a broad ancestor term that adds no specificity beyond GO:0005524 (ATP binding) and GO:0016887 (ATP hydrolysis activity).
Supporting Evidence:
file:VARPD/pstB/pstB-uniprot.txt
FT BINDING 45..52 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /evidence="ECO:0000256|PROSITE-ProRule:PRU00434"
GO:0005315 phosphate transmembrane transporter activity
IEA
GO_REF:0000002 		MARK AS OVER ANNOTATED
Summary: PstB is the cytoplasmic ATP-hydrolyzing motor subunit of the PstSCAB importer rather than the transmembrane pore; it contributes energy coupling to the holocomplex ATPase-coupled phosphate transporter activity.
Reason: Following the curation convention for ECOLI/pstB (UniProtKB:P0AAH0), PstB directly catalyzes ATP hydrolysis (GO:0016887) and contributes to the holocomplex ATPase-coupled phosphate ion transmembrane transporter activity (GO:0015415, captured in core_functions), but does not by itself form the transmembrane phosphate translocation channel.
Supporting Evidence:
file:VARPD/pstB/pstB-uniprot.txt
DR InterPro; IPR005670; PstB-like. DR NCBIfam; TIGR00972; 3a0107s01c2; 1. DR PANTHER; PTHR43423; ABC TRANSPORTER I FAMILY MEMBER 17; 1. DR PANTHER; PTHR43423:SF3; PHOSPHATE IMPORT ATP-BINDING PROTEIN PSTB; 1.
GO:0005524 ATP binding
IEA
GO_REF:0000120 		KEEP AS NON CORE
Summary: Supported cosubstrate-binding activity at the Walker A P-loop (45-GPSGCGKS-52), retained as non-core alongside the core catalytic term GO:0016887 (ATP hydrolysis activity).
Reason: PstB binds ATP via its conserved Walker A P-loop (residues 45-52; PROSITE PS50893, PMID:2646285). Matching ECOLI/pstB, GO:0005524 is retained as KEEP_AS_NON_CORE because GO:0016887 (ATP hydrolysis activity) is the more informative core molecular function of the ABC motor subunit.
Supporting Evidence:
file:VARPD/pstB/pstB-uniprot.txt
FT BINDING 45..52 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /evidence="ECO:0000256|PROSITE-ProRule:PRU00434"
PMID:2646285
The residues Gly-48 and Lys-49 are key residues in the putative nucleotide-binding site.
GO:0005886 plasma membrane
IEA
GO_REF:0000044 		ACCEPT
Summary: Core subcellular localization; PstB associates peripherally with the cytoplasmic face of the inner (plasma) membrane as part of the PstSCAB transporter complex.
Reason: PstB is a peripheral inner-membrane protein that docks onto the cytoplasmic coupling helices of PstC and PstA and interacts with membrane-associated PhoU at the bacterial plasma membrane (PMID:2646285, PMID:24563032; matching ECOLI/pstB).
Supporting Evidence:
PMID:2646285
The pstB gene encodes a peripheral membrane protein of the Pst system which carries a putative nucleotide-binding site.
GO:0016020 membrane
IEA
GO_REF:0000002 		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:
PMID:2646285
The pstB gene encodes a peripheral membrane protein of the Pst system which carries a putative nucleotide-binding site.
GO:0016887 ATP hydrolysis activity
IEA
GO_REF:0000002 		ACCEPT
Summary: Core molecular function of PstB as the ATP-hydrolyzing motor subunit of the PstSCAB ABC phosphate importer.
Reason: PstB contains the complete ABC ATPase catalytic machinery (Walker A 45-GPSGCGKS-52, ABC signature 156-LSGGQQQRLCIAR-168, Walker B Glu181 in 176-VLLLDEPCSALD-187, switch His212; PROSITE PS50893, CDD cd03260) that hydrolyzes ATP to power orthophosphate import across the inner membrane (PMID:2646285, PMID:24563032; matching ECOLI/pstB).
Supporting Evidence:
file:VARPD/pstB/pstB-uniprot.txt
FT DOMAIN 13..254 FT /note="ABC transporter" FT /evidence="ECO:0000259|PROSITE:PS50893" FT BINDING 45..52 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /evidence="ECO:0000256|PROSITE-ProRule:PRU00434"
PMID:2646285
The amino acid substitutions Gly-48----Ile and Lys-49----Gln, resulting from the pstB mutations, caused the loss of phosphate transport through the Pst system and the derepression of alkaline phosphatase activity. The residues Gly-48 and Lys-49 are key residues in the putative nucleotide-binding site.
GO:0035435 phosphate ion transmembrane transport
IEA
GO_REF:0000002 		ACCEPT
Summary: Core biological process; PstB supplies the ATP hydrolysis energy required for orthophosphate import through the PstSCAB complex.
Reason: VPARA_10450 belongs to the canonical PstB phosphate-import ATPase family (InterPro IPR005670, CDD cd03260, NCBIfam TIGR00972, PANTHER PTHR43423:SF3) and is encoded between pstA and phoU in the V. paradoxus TBEA6 PstSCAB operon (PMID:3881386, PMID:2646285, PMID:24563032).
Supporting Evidence:
file:VARPD/pstB/pstB-uniprot.txt
DR InterPro; IPR005670; PstB-like. DR NCBIfam; TIGR00972; 3a0107s01c2; 1. DR PANTHER; PTHR43423; ABC TRANSPORTER I FAMILY MEMBER 17; 1. DR PANTHER; PTHR43423:SF3; PHOSPHATE IMPORT ATP-BINDING PROTEIN PSTB; 1.
PMID:2646285
The amino acid substitutions Gly-48----Ile and Lys-49----Gln, resulting from the pstB mutations, caused the loss of phosphate transport through the Pst system and the derepression of alkaline phosphatase activity.
GO:0055052 ATP-binding cassette (ABC) transporter complex, substrate-binding subunit-containing
IC
file:VARPD/pstB/pstB-uniprot.txt 		NEW
Summary: PstB is the dimeric cytoplasmic ATPase subunit of the substrate-binding-protein-dependent PstSCAB ABC importer complex.
Reason: Inferred by curator (IC) from PstB domain classification in file:VARPD/pstB/pstB-uniprot.txt and co-organization with pstS, pstC, and pstA (VPARA_10460-VPARA_10480) on contig JZWI01000005 (PMID:3881386, PMID:24563032; matching ECOLI/pstB).
Supporting Evidence:
file:VARPD/pstB/pstB-uniprot.txt
DR InterPro; IPR005670; PstB-like. DR NCBIfam; TIGR00972; 3a0107s01c2; 1. DR PANTHER; PTHR43423; ABC TRANSPORTER I FAMILY MEMBER 17; 1. DR PANTHER; PTHR43423:SF3; PHOSPHATE IMPORT ATP-BINDING PROTEIN PSTB; 1.
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

Hydrolyzes ATP as the dimeric cytoplasmic motor subunit of the PstSCAB complex, contributing energy coupling to ATPase-coupled orthophosphate transmembrane import across the bacterial plasma membrane.

Molecular Function:
ATP hydrolysis activity
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/pstB/pstB-uniprot.txt
    FT DOMAIN 13..254 FT /note="ABC transporter" FT /evidence="ECO:0000259|PROSITE:PS50893" FT BINDING 45..52 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /evidence="ECO:0000256|PROSITE-ProRule:PRU00434"
  • PMID:2646285
    The amino acid substitutions Gly-48----Ile and Lys-49----Gln, resulting from the pstB mutations, caused the loss of phosphate transport through the Pst system and the derepression of alkaline phosphatase activity.
  • 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: How does ATP binding versus hydrolysis at the PstB (VPARA_10450) dimer interface remodel its interaction with PhoU (VPARA_10440) to toggle PhoR1 (VPARA_10420) between its kinase and phosphatase states?

Suggested experts: McCleary WR

Suggested Experiments

Experiment: Purify recombinant Variovorax paradoxus PstB (A0A0D0L7E0) and PhoU (A0A0H2MBK2) and quantify their interaction in the presence of ATP, ADP, and non-hydrolyzable ATP-gamma-S by pull-down and size-exclusion chromatography.

Hypothesis: PstB forms a nucleotide-state-dependent complex with PhoU that is stabilized in the high-phosphate transport conformation (PMID:24563032).

📚 Additional Documentation

Notes

(pstB-notes.md)

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