InterPro domain: IPR018389

The tripartite ATP-independent periplasmic (TRAP) transporters are substrate-binding protein (SBP)-dependent secondary transporters found in prokaryotes. They consist of a substrate-binding protein (SBP) of the DctP or TAXI families and two integral membrane proteins that form the DctQ and DctM protein families [ 1 ].

This entry represents the DctP family of the substrate-binding proteins. They are part of the DctP-TRAP (tripartite ATP-independent periplasmic) transporter involved in binding extracellular solutes for transport across the bacterial cytoplasmic membrane. Proteins in this family include DctP from R. capsulatus, SiaP from Haemophilus influenzae [ 2 ], DctB from Bacillus subtilis [ 2 ], and TeaA from Halomonas elongata [ 3 ]. The structure of the SiaP receptor has revealed an overall topology similar to ATP binding cassette ESR (extracytoplasmic solute receptors) proteins [ 4 ]. Upon binding of sialic acid, SiaP undergoes domain closure about a hinge region and kinking of an alpha-helix hinge component [ 5 ].

1. Tripartite ATP-independent periplasmic (TRAP) transporters in bacteria and archaea. FEMS Microbiol. Rev. 35, 68-86
2. Regulation of the transport system for C4-dicarboxylic acids in Bacillus subtilis. Microbiology (Reading, Engl.) 146 ( Pt 2), 263-71
3. 1.55 A structure of the ectoine binding protein TeaA of the osmoregulated TRAP-transporter TeaABC from Halomonas elongata. Biochemistry 47, 9475-85
4. Conservation of structure and mechanism in primary and secondary transporters exemplified by SiaP, a sialic acid binding virulence factor from Haemophilus influenzae. J. Biol. Chem. 281, 22212-22