@article{mbs:/content/journal/micro/10.1099/00221287-145-12-3431, author = "Rabus, Ralf and Jack, Donald L. and Kelly, David J. and Saier, Jr, Milton H.", title = "TRAP transporters: an ancient family of extracytoplasmic solute- receptor-dependent secondary active transporters ", journal= "Microbiology", year = "1999", volume = "145", number = "12", pages = "3431-3445", doi = "https://doi.org/10.1099/00221287-145-12-3431", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-145-12-3431", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", keywords = "dicarboxylates", keywords = "gb, GenBank", keywords = "molecular evolution ", keywords = "sp, SWISS-PROT", keywords = "TC, transport classification", keywords = "phylogeny", keywords = "TMS, transmembrane spanning α-helix", keywords = "TRAP-T family ", keywords = "TRAP-T, tripartite ATP-independent periplasmic transporters", keywords = "ion transport", keywords = "IT, ion transporter", keywords = "p.m.f., protonmotive force", abstract = "Tripartite ATP-independent periplasmic transporters (TRAP-T) represent a novel type of secondary active transporter that functions in conjunction with an extracytoplasmic solute-binding receptor. The best characterized TRAP-T family member is from Rhodobacter capsulatus and is specific for C4-dicarboxylates [Forward, J. A., Behrendt, M. C., Wyborn, N. R., Cross, R. & Kelly, D. J. (1997). J Bacteriol 179, 5482–5493]. It consists of three essential proteins, DctP, a periplasmic C4-dicarboxylate-binding receptor, and two integral membrane proteins, DctM and DctQ, which probably span the membrane 12 and 4 times, respectively. Homologues of DctM, DctP and DctQ were identified in all major bacterial subdivisions as well as in archaea. An orphan DctP homologue in the Gram-positive bacterium Bacillus subtilis may serve as a receptor for a two- component transcriptional regulatory system rather than as a constituent of a TRAP-T system. Phylogenetic data suggest that all present day TRAP-T systems probably evolved from a single ancestral transporter with minimal shuffling of constituents between systems. Homologous TRAP-T constituents exhibit decreasing degrees of sequence identity in the order DctM>DctP>DctQ. DctM appears to belong to a large superfamily of transporters, the ion transporter (IT) superfamily, one member of which can function by either protonmotive force- or ATP-dependent energization. It is proposed that IT superfamily members exhibit the unusual capacity to function in conjunction with auxiliary proteins that modify the transport process by providing (i) high-affinity solute reception, (ii) altered energy coupling and (iii) additional yet to be defined functions.", }