Curatorial Notes for phoR1 (A0A0H2MMT2, VPARA_10420) in Variovorax paradoxus TBEA6

1. Gene & Protein Identity

• UniProt Accession: A0A0H2MMT2 (A0A0H2MMT2_VARPD)
• Gene Symbol: phoR1
• Locus Tag / EMBL CDS: VPARA_10420 / KLN58030.1 on contig JZWI01000005 (RefSeq:WP_021007059.1)
• Protein Length: 464 aa (50,842 Da); inner-membrane bifunctional sensor histidine kinase / phospho-PhoB1 phosphatase (EC 2.7.13.3).
• Domain Architecture & Active Sites:
• N-terminal transmembrane anchor (FT TRANSMEM 29..45 / PhoR N-terminal transmembrane domain Pfam:PF11808 PhoR, InterPro:IPR021766 PhoR_N).
• Cytoplasmic Per-ARNT-Sim (PAS) sensory domain (Pfam:PF00989 PAS, CDD:cd00130, InterPro:IPR000014 / IPR013767), which directly interacts with PhoU (VPARA_10440) to sense the PstSCAB phosphate-transport state (PMID:24563032).
• Histidine kinase dimerization/phosphoacceptor (DHp, HisKA, Pfam:PF00512, CDD:cd00082, InterPro:IPR003661) and catalytic ATP-binding (HATPase_c, Pfam:PF02518, InterPro:IPR003594) domains (FT DOMAIN 216..436 /note="Histidine kinase", PROSITE:PS50109), with the invariant autocatalytic phosphohistidine acceptor His219 (FT MOD_RES 219 /note="Phosphohistidine; by autocatalysis" within 216-NVSHEIRTPL-225).
• Full-length orthology: NCBIfam:TIGR02966 (phoR_proteo), InterPro:IPR014310 (Sig_transdc_His_kinase_PhoR), PANTHER:PTHR45453:SF1 (PHOSPHATE REGULON SENSOR PROTEIN PHOR).

2. Operon Context on Contig JZWI01000005

• Encoded immediately adjacent to phoB1 (VPARA_10430, KLN58031.1) at the boundary of the phoR1-phoB1-phoU-pstB-pstA-pstC-pstS-ppx (VPARA_10420–VPARA_10490) phosphate regulon gene cluster.

3. Literature & Comparative Evidence

• PMID:24563032 (Gardner et al. 2014 J Bacteriol): Establishes that PhoR is an integral inner-membrane bifunctional histidine autokinase and phospho-PhoB phosphatase whose cytoplasmic PAS domain physically interacts with PhoU to switch between phosphatase activity (under high external $\text{P}_i$, when PstSCAB is in its high-activity state) and autokinase/phosphotransferase activity (under limiting external $\text{P}_i$).

4. Annotation Review Decisions

• GO:0000155 (phosphorelay sensor kinase activity, IEA GO_REF:0000120): ACCEPT — core MF (PROSITE:PS50109 216..436, His219 phosphohistidine site).
• GO:0000160 (phosphorelay signal transduction system, IEA GO_REF:0000002): ACCEPT — core BP.
• GO:0004673 (protein histidine kinase activity, IEA GO_REF:0000120): TOO_GENERAL — parent of GO:0000155.
• GO:0004721 (phosphoprotein phosphatase activity, IEA GO_REF:0000120): ACCEPT — core second catalytic activity of bifunctional PhoR1 toward phospho-PhoB1 under phosphate-replete conditions (PMID:24563032).
• GO:0005886 (plasma membrane, IEA GO_REF:0000120): ACCEPT — core CC (FT TRANSMEM 29..45).
• GO:0006355 (regulation of DNA-templated transcription, IEA GO_REF:0000002): KEEP_AS_NON_CORE — PhoR1 regulates transcription indirectly upstream of its response regulator partner PhoB1.
• GO:0007165 (signal transduction, IEA GO_REF:0000120): TOO_GENERAL — entailed by GO:0000160.
• GO:0016020 (membrane, IEA GO_REF:0000002): TOO_GENERAL — entailed by GO:0005886.
• GO:0016036 (cellular response to phosphate starvation, IEA GO_REF:0000118): ACCEPT — core BP.
• GO:0016301 (kinase activity, IEA GO_REF:0000104): TOO_GENERAL — entailed by GO:0000155.
• GO:0016740 (transferase activity, IEA GO_REF:0000104): TOO_GENERAL — entailed by GO:0000155.
• GO:0016772 (transferase activity, transferring phosphorus-containing groups, IEA GO_REF:0000002): TOO_GENERAL — entailed by GO:0000155.