Summary: Tripartite tricarboxylate transporter family receptor
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Tripartite tricarboxylate transporter family receptor Provide feedback
These probable extra-cytoplasmic solute receptors are strongly overrepresented in several beta-proteobacteria . This family, formerly known as Bug - Bordetella uptake gene (bug) product - is a family of bacterial tripartite tricarboxylate receptors of the extracytoplasmic solute binding receptor-dependent transporter group of families, distinct from the ABC and TRAP-T families . The TctABC system has been characterised in S. typhimurium  and TctC is the extracytoplasmic tricarboxylate-binding receptor which binds the transporters TctA and TctB, two integral membrane proteins. Complete three-component systems are found only in bacteria .
Antoine R, Jacob-Dubuisson F, Drobecq H, Willery E, Lesjean S, Locht C; , J Bacteriol 2003;185:1470-1474.: Overrepresentation of a gene family encoding extracytoplasmic solute receptors in Bordetella. PUBMED:12562821 EPMC:12562821
Sweet GD, Kay CM, Kay WW; , J Biol Chem. 1984;259:1586-1592.: Tricarboxylate-binding proteins of Salmonella typhimurium. Purification, crystallization, and physical properties. PUBMED:6141166 EPMC:6141166
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR005064
Bordetella pertussis, the causative agent of human whooping cough (pertussis), is an obligate human pathogen with diverse high-affinity transport systems for the assimilation of iron, a biometal that is essential for growth [PUBMED:17724074]. Periplasmic binding proteins of a new family, particularly well represented in this organism (and more generally in beta-proteobacteria), have been called Bug receptors [PUBMED:16403514].
They adopt a characteristic Venus flytrap fold with two globular domains bisected by a ligand-binding cleft. The family is specific for carboxylated solutes, with a characteristic mode of binding involving two highly conserved beta strand-beta turn-alpha helix motifs originating from each domain. These two motifs form hydrogen bonds with a carboxylate group of the ligand, both directly and via conserved water molecules, and have thus been termed the carboxylate pincers. Domain 1 recognises the ligand and the carboxylate group serves as an initial anchoring point. Domain 2 discriminates between productively and non-productively bound ligands as proper interactions with this domain is needed for the of the closed conformation [PUBMED:17870093].
BugE has a glutamate bound ligand. No charged residues are involved in glutamate binding by BugE, unlike what has been described for all glutamate receptors reported so far. The Bug architecture is highly conserved despite limited sequence identity [PUBMED:17057341].
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|Cellular component||outer membrane-bounded periplasmic space (GO:0030288)|
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Periplasmic binding proteins (PBPs) consist of two large lobes that close around the bound ligand. This architecture is reiterated in transcriptional regulators, such as the lac repressors. In the process of evolution, genes encoding the PBPs have fused with genes for integral membrane proteins. Thus, diverse mammalian receptors contain extracellular ligand binding domains that are homologous to the PBPs; these include glutamate/glycine-gated ion channels such as the NMDA receptor, G protein-coupled receptors, including metabotropic glutamate, GABA-B, calcium sensing, and pheromone receptors, and atrial natriuretic peptide-guanylate cyclase receptors .
The clan contains the following 23 members:DUF3834 HisG Lig_chan-Glu_bd Lipoprotein_8 Lipoprotein_9 LysR_substrate Mycoplasma_p37 NMT1 NMT1_2 OpuAC PBP_like PBP_like_2 Phosphonate-bd SBP_bac_1 SBP_bac_11 SBP_bac_3 SBP_bac_5 SBP_bac_6 SBP_bac_7 SBP_bac_8 TctC Transferrin VitK2_biosynth
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Curation and family details
|Seed source:||Pfam-B_3343 (release 6.6)|
|Previous IDs:||UPF0065; Bug;|
|Number in seed:||9|
|Number in full:||6762|
|Average length of the domain:||269.60 aa|
|Average identity of full alignment:||28 %|
|Average coverage of the sequence by the domain:||83.24 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||9|
|Download:||download the raw HMM for this family|
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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the TctC domain has been found. There are 7 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
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