Curatorial Notes for pstA (A0A0H2M6I3, VPARA_10460) in Variovorax paradoxus TBEA6

1. Gene & Protein Identity

• UniProt Accession: A0A0H2M6I3 (A0A0H2M6I3_VARPD)
• Gene Symbol: pstA
• Locus Tag / EMBL CDS: VPARA_10460 / KLN58034.1 on contig JZWI01000005 (RefSeq:WP_080966475.1)
• Protein Length: 294 aa (31,555 Da); 6 transmembrane helices (30..51, 79..102, 123..144, 150..169, 205..223, 267..289) and an ABC transmembrane type-1 domain (PROSITE:PS50928 at 83..286, Pfam:PF00528 BPD_transp_1, CDD:cd06261 TM_PBP2).
• Specific Family & Active-Site Conservation:
• InterPro:IPR005672 (Phosphate_PstA), NCBIfam:TIGR00974 (3a0107s02c), NCBIfam:NF008430 (pstA), PANTHER:PTHR42922:SF1 (PHOSPHATE TRANSPORT SYSTEM PERMEASE PROTEIN PSTA).
• Conserves Arg220 and Glu224 within 219-ARIAGETA-226 (corresponding to E. coli PstA Arg220, whose mutation Arg220Gln abolishes phosphate transport through PstSCAB in PMID:2896188).

2. Operon Context on Contig JZWI01000005

• Encoded between pstB (VPARA_10450, KLN58033.1) and pstC (VPARA_10470, KLN58035.1) within the phoR1-phoB1-phoU-pstB-pstA-pstC-pstS-ppx (VPARA_10420–VPARA_10490) phosphate regulon gene cluster.

3. Literature & Comparative Evidence

• PMID:2896188 (Cox et al. 1988 J Bacteriol): Site-directed mutagenesis demonstrates that Arg220 of E. coli PstA is essential for orthophosphate translocation through the Pst system.
• PMID:3881386 (Surin et al. 1985 J Bacteriol): Complete sequence of the phoS-pstC-pstA-pstB-phoU operon.
• PMID:24563032 (Gardner et al. 2014 J Bacteriol): Subunit architecture of PstSCAB and coupling to PhoU and PhoR.

4. Annotation Review Decisions

• Following ECOLI/pstA (P0AGH5) and ECOLI/pstC (P0AGH8):
• GO:0005315 (phosphate transmembrane transporter activity, IEA GO_REF:0000002, enables): MARK_AS_OVER_ANNOTATED — PstA is one of two heterodimeric transmembrane permease subunits (with PstC) of the PstSCAB complex; its contributes_to relationship to GO:0015415 (ATPase-coupled phosphate ion transmembrane transporter activity) is captured in core_functions.contributes_to_molecular_function.
• GO:0005886 (plasma membrane, IEA GO_REF:0000120): ACCEPT — core location of this 6-pass inner-membrane permease subunit.
• GO:0016020 (membrane, IEA GO_REF:0000120): TOO_GENERAL — entailed by GO:0005886.
• GO:0035435 (phosphate ion transmembrane transport, IEA GO_REF:0000002): ACCEPT — core biological process.
• GO:0043190 (ATP-binding cassette (ABC) transporter complex, IEA GO_REF:0000104): MODIFY -> GO:0055052 (ATP-binding cassette (ABC) transporter complex, substrate-binding subunit-containing).
• GO:0055085 (transmembrane transport, IEA GO_REF:0000002): TOO_GENERAL — entailed by GO:0035435.
• GO:0055052 (ATP-binding cassette (ABC) transporter complex, substrate-binding subunit-containing, IC from file:VARPD/pstA/pstA-uniprot.txt): NEW.