Taurine transport system permease protein TauC (VPARA_03670, A0A0H2M7Y1) in Variovorax paradoxus strain TBEA6 is a 294-amino-acid multi-pass integral inner-membrane subunit (InterPro IPR000515, PANTHER PTHR30151:SF25) of the TauABC ATP-binding cassette (ABC) taurine importer complex. Encoded at the 3' end of the syntenic tauA-tauB1-tauC (VPARA_03650-VPARA_03670) operon on genomic contig JZWI01000003 (consecutive EMBL CDS accessions KLN58254.1-KLN58256.1) immediately downstream of the periplasmic binding protein tauA (VPARA_03650, KLN58254.1) and the ATPase subunit tauB1 (VPARA_03660, KLN58255.1), TauC contains six predicted transmembrane alpha-helices (residues 42-62, 100-121, 141-160, 166-185, 221-241, and 261-283) and a conserved ABC transmembrane type-1 domain (PROSITE PS50928, Pfam PF00528, residues 100-280) that forms the membrane translocation pathway for importing taurine into the cytoplasm.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005886 plasma membrane | IEA GO_REF:0000120 | ACCEPT | Summary: Core subcellular localization supported by the six transmembrane alpha-helices and the ABC transmembrane type-1 domain (PROSITE PS50928, residues 100-280). Reason: TauC is a multi-pass integral inner-membrane protein containing six transmembrane helices (residues 42-62, 100-121, 141-160, 166-185, 221-241, and 261-283) and an ABC transmembrane type-1 domain (PROSITE PS50928, PROSITE-ProRule PRU00441, RuleBase RU363032, residues 100-280) embedded in the bacterial plasma membrane. Supporting Evidence: file:VARPD/tauC/tauC-uniprot.txt CC -!- SUBCELLULAR LOCATION: Cell membrane {ECO:0000256|ARBA:ARBA00004651, CC ECO:0000256|RuleBase:RU363032}; Multi-pass membrane protein CC {ECO:0000256|ARBA:ARBA00004651, ECO:0000256|RuleBase:RU363032}. |
| GO:0010438 cellular response to sulfur starvation | IEA GO_REF:0000118 | KEEP AS NON CORE | Summary: Valid physiological context because the tauABCD system is induced under sulfate/cysteine starvation, retained as non-core relative to TauC's direct taurine transport role. Reason: Expression of the bacterial tauABC taurine uptake system is induced under sulfate starvation to scavenge organosulfur (PMID:8808933, PMID:10781534); GO:0010438 (cellular response to sulfur starvation) is retained as KEEP_AS_NON_CORE while TauC's direct transport role is captured by GO:0015734 (taurine transmembrane transport). Supporting Evidence: PMID:10781534 The Escherichia coli tauABCD and ssuEADCB gene clusters are required for the utilization of taurine and alkanesulfonates as sulfur sources and are expressed only under conditions of sulfate or cysteine starvation. |
| 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 true of TauC but adds no specificity beyond GO:0005886 (plasma membrane) already accepted in this review. Supporting Evidence: file:VARPD/tauC/tauC-uniprot.txt FT DOMAIN 100..280 FT /note="ABC transmembrane type-1" FT /evidence="ECO:0000259|PROSITE:PS50928" |
| GO:0042918 alkanesulfonate transmembrane transport | IEA GO_REF:0000117 | MODIFY | Summary: Correct but general parent process; refine to the specific child term GO:0015734 (taurine transmembrane transport) based on PANTHER PTHR30151:SF25 and syntenic placement in the tauA-tauB1-tauC operon. Reason: ARBA annotates the broader parent term GO:0042918 (alkanesulfonate transmembrane transport). Because TauC belongs specifically to PANTHER PTHR30151:SF25 (TAURINE TRANSPORT SYSTEM PERMEASE PROTEIN TAUC) and is co-encoded at the 3' end of the tauA-tauB1-tauC (VPARA_03650-VPARA_03670) operon on contig JZWI01000003, GO:0042918 is refined to its specific descendant term GO:0015734 (taurine transmembrane transport; PMID:8808933, PMID:10781534). Proposed replacements: taurine transmembrane transport Supporting Evidence: file:VARPD/tauC/tauC-uniprot.txt DR PANTHER; PTHR30151:SF25; TAURINE TRANSPORT SYSTEM PERMEASE PROTEIN TAUC; 1. PMID:8808933 We therefore suggest that the proteins encoded by tauABC constitute an uptake system for taurine and that the product of tauD is involved in the oxygenolytic release of sulfite from taurine. |
| GO:0043190 ATP-binding cassette (ABC) transporter complex | IEA GO_REF:0000104 | MODIFY | Summary: Correct but general complex term; refine to GO:0055052 (ATP-binding cassette (ABC) transporter complex, substrate-binding subunit-containing) for this bacterial binding-protein-dependent TauABC importer. Reason: TauC (VPARA_03670, KLN58256.1) is a binding-protein-dependent ABC importer permease (RuleBase RU363032, PANTHER PTHR30151:SF25) encoded immediately downstream of the periplasmic binding subunit tauA (VPARA_03650, KLN58254.1) and the ATPase subunit tauB1 (VPARA_03660, KLN58255.1) on contig JZWI01000003, so GO:0043190 is refined to its more specific descendant GO:0055052 (ATP-binding cassette (ABC) transporter complex, substrate-binding subunit-containing; PMID:8808933, PMID:10781534). Proposed replacements: ATP-binding cassette (ABC) transporter complex, substrate-binding subunit-containing Supporting Evidence: file:VARPD/tauC/tauC-uniprot.txt CC -!- SIMILARITY: Belongs to the binding protein-dependent transport system CC permease family. {ECO:0000256|RuleBase:RU363032}. PMID:8808933 We therefore suggest that the proteins encoded by tauABC constitute an uptake system for taurine and that the product of tauD is involved in the oxygenolytic release of sulfite from taurine. |
| GO:0055085 transmembrane transport | IEA GO_REF:0000002 | MODIFY | Summary: Correct but general biological process; refine to GO:0015734 (taurine transmembrane transport) based on PANTHER PTHR30151:SF25 and syntenic co-localization in the tauA-tauB1-tauC operon. Reason: GO:0055085 (transmembrane transport) is true of TauC but overly general; classification in PANTHER PTHR30151:SF25 (TAURINE TRANSPORT SYSTEM PERMEASE PROTEIN TAUC) and co-localization in the tauA-tauB1-tauC operon (VPARA_03650-VPARA_03670) support refinement to GO:0015734 (taurine transmembrane transport; PMID:8808933). Proposed replacements: taurine transmembrane transport Supporting Evidence: file:VARPD/tauC/tauC-uniprot.txt DR PANTHER; PTHR30151:SF25; TAURINE TRANSPORT SYSTEM PERMEASE PROTEIN TAUC; 1. PMID:8808933 We therefore suggest that the proteins encoded by tauABC constitute an uptake system for taurine and that the product of tauD is involved in the oxygenolytic release of sulfite from taurine. |
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Download this section (compressed HTML)Q: Does Variovorax paradoxus TauC (VPARA_03670) form a homodimeric pore within the TauAB1C complex, and how do its periplasmic loops engage taurine-loaded TauA (VPARA_03650)?
Suggested experts: Kertesz MA, Leisinger T
Experiment: Construct an in-frame ΞtauC (VPARA_03670) deletion in Variovorax paradoxus TBEA6 and measure [14C]-taurine uptake and taurine-dependent growth under sulfate starvation.
Hypothesis: Deletion of tauC abolishes high-affinity taurine uptake and prevents growth on taurine as a sole sulfur source.
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