HptB (PA3345) is a 116-aa stand-alone histidine-containing phosphotransfer (HPt) protein of Pseudomonas aeruginosa, related to yeast Ypd1 and plant AHPs, with the phospho-accepting histidine at position 57. It receives phosphoryl groups from several hybrid sensor kinases (PA1611, PA1976, PA2824 and RetS) and passes them to the response regulator HsbR (PA3346), whose PP2C phosphatase and kinase/anti-sigma domains control phosphorylation of the anti-anti-sigma factor HsbA (PA3347). Through this partner-switch cascade HptB signalling governs the FlgM-FliA flagellar sigma pair, the HsbR-RpoS interaction, the HsbD diguanylate cyclase and GacA-dependent rsmY expression. An hptB deletion forms a Pel-dependent hyperbiofilm, attaches and twitches more, and swims and swarms poorly, so HptB promotes the planktonic, motile state.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000160 phosphorelay signal transduction system | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from the HPt node PTN002000688, seeded by yeast, fungal, plant and Dictyostelium HPt proteins. Reason: HptB is the phosphotransfer intermediate of a multistep phosphorelay from hybrid sensors to HsbR. Supporting Evidence: PMID:18256026 Among the 12 recombinant orphan sensor kinases tested, 4 of these sensors (PA1611, PA1976, PA2824, and RetS) transferred the phosphoryl group to HptB (PA3345). |
| GO:0000160 phosphorelay signal transduction system | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro HPt domain mapping. Reason: Same claim as the IBA row. Supporting Evidence: PMID:16182517 We herein demonstrate that the hybrid sensor PA1611 carries out specific signal transduction, through HptB (PA3345), to the response regulator PA3346 in Pseudomonas aeruginosa PAO1. |
| GO:0004672 protein kinase activity | IEA GO_REF:0000117 | TOO GENERAL | Summary: ARBA prediction of a generic protein kinase activity. Reason: In GO, GO:0009927 histidine phosphotransfer kinase activity, accepted here, is_a GO:0004672, so this row is entailed and adds nothing. HptB has no kinase domain; it relays phosphoryl groups through His57. |
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | ACCEPT | Summary: IBA cytoplasm from PTN002000688. Reason: A 116-aa soluble HPt protein with no signal peptide or TM segment, shuttling between membrane sensors and the cytoplasmic regulator HsbR; cytoplasm is as precise as warranted. Supporting Evidence: PMID:22128156 The histidine-containing phosphotransfer protein-B (HptB; PA3345) is an intermediate protein involved in transferring a phosphoryl group from multiple sensor kinases to the response regulator PA3346 in Pseudomonas aeruginosa PAO1. |
| GO:0009927 histidine phosphotransfer kinase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from the 9-seed PTN002000688 IBD; this gene appears among its sources because of its own IDA row, which is expected. Reason: Core activity. The IBD stands on the plant AHPs, S. pombe Mpr1, A. nidulans YpdA and Dictyostelium RdeA, and HptB's own phosphotransfer is shown in vitro. Supporting Evidence: PMID:18256026 Among the 12 recombinant orphan sensor kinases tested, 4 of these sensors (PA1611, PA1976, PA2824, and RetS) transferred the phosphoryl group to HptB (PA3345). file:PSEAE/PA3345/PA3345-uniprot.txt FT MOD_RES 57 FT /note="Phosphohistidine" FT /evidence="ECO:0000256|PROSITE-ProRule:PRU00110" |
| GO:0009927 histidine phosphotransfer kinase activity | IDA PMID:16182517 Identification of an HptB-mediated multi-step phosphorelay i... | ACCEPT | Summary: PseudoCAP IDA and one of 9 seeds of PTN002000688. The paper demonstrates signal transfer from PA1611 through HptB to PA3346. Reason: Seed verdict SOUND. The abstract states the phosphorelay result, and the same group's follow-up shows in vitro phosphotransfer from four sensors to HptB and on to PA3346. Supporting Evidence: PMID:16182517 We herein demonstrate that the hybrid sensor PA1611 carries out specific signal transduction, through HptB (PA3345), to the response regulator PA3346 in Pseudomonas aeruginosa PAO1. PMID:18256026 Interestingly, the phosphoryl groups from these sensors all appeared to be transferred via HptB to PA3346 |
| GO:0043424 protein histidine kinase binding | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: IBA from PTN002000688; HptB interacts with four hybrid sensor kinases in two-hybrid assays. Reason: True and gene-specifically supported, but the binding is part of the phosphotransfer activity captured by GO:0009927 rather than a separate function. Supporting Evidence: PMID:18256026 The in vivo interaction between HptB and each of the sensors was also confirmed using the bacterial two-hybrid assay. |
| GO:0050921 positive regulation of chemotaxis | IMP PMID:16182517 Identification of an HptB-mediated multi-step phosphorelay i... | KEEP AS NON CORE | Summary: PseudoCAP IMP; the abstract implicates the pathway in the chemotaxis response. Reason: The abstract names chemotaxis among the phenotypes of the hptB deletion but not the sign; deferring to the curator, who read the paper. A downstream regulatory output of the phosphorelay, not a core function. Supporting Evidence: PMID:16182517 As assessed by phenotypic changes in the hptB deletion mutant, the pathway is likely to be involved in the regulation of flagellar activity, the chemotaxis response, twitching motility, and biofilm formation in the bacteria. |
| GO:1900191 negative regulation of single-species biofilm formation | IMP PMID:16182517 Identification of an HptB-mediated multi-step phosphorelay i... | ACCEPT | Summary: PseudoCAP IMP. The hptB deletion forms a hyperbiofilm, complemented in trans. Reason: Well supported by several independent studies; repression of the Pel biofilm via GacA/rsmY, HsbD and RpoS is the main physiological output of HptB signalling. Supporting Evidence: PMID:20398205 Introduction of the hptB gene cloned in the pUCP18 plasmid (pUCPhptB), into the hptB mutant (PAKΞhptB), resulted in restoration of biofilm and polysaccharide production PMID:27792789 When compared to wild type, the hptB mutant produces more exopolysaccharides [17], attaches more easily to surface, increases twitching motility while it decreases swimming and swarming movements (Figs 2 and 4β6). |
| GO:2000145 regulation of cell motility | IMP PMID:16182517 Identification of an HptB-mediated multi-step phosphorelay i... | ACCEPT | Summary: PseudoCAP IMP; hptB affects flagellar and twitching motility with opposite signs. Reason: HptB promotes swimming and swarming and restrains twitching, so the unsigned parent is the right level for this row. Supporting Evidence: PMID:27792789 When compared to wild type, the hptB mutant produces more exopolysaccharides [17], attaches more easily to surface, increases twitching motility while it decreases swimming and swarming movements (Figs 2 and 4β6). |
Loading supporting contentβ¦
Download this section (compressed HTML)Experiment: Test reverse phosphotransfer from phospho-HsbR receiver domain to HptB and to each sensor in vitro, and measure HptB phosphorylation in vivo (Phos-tag) under biofilm- and motility-inducing conditions.
What is not known β curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: The signals sensed by PA1611, PA1976, PA2824 and RetS that are integrated through HptB, and whether HptB phosphotransfer is reversible (acting as a phosphate sink), are unknown.
BIOLOGY
Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)