Caught in a TRAP: Substrate-binding proteins in secondary transport

TY - JOUR

T1 - Caught in a TRAP

T2 - Substrate-binding proteins in secondary transport

AU - Fischer, Marcus

AU - Zhang, Qian Yi

AU - Hubbard, Roderick E.

AU - Thomas, Gavin H.

N1 - Funding Information: G.H.T. would like to acknowledge continued funding from the Biotechnology and Biological Sciences Research Council (BBSRC) and we are indebted to the Wild Fund and BBSRC for supporting M.F.

PY - 2010/10

Y1 - 2010/10

N2 - Substrate-binding protein (SBP)-dependent secondary transporters are ubiquitous in prokaryotes yet poorly characterised. Recently, the structures of over 10 prokaryotic SBPs have been solved, which we compare here to consider their impact on our understanding of transporter function and evolution. Seven structures are from tripartite ATP-independent periplasmic (TRAP) transporters of the DctP-type, which have similar overall structures distinct from SBPs used by ATP-binding cassette (ABC) transporters, despite recognising a range of substrates. A defining feature of substrate recognition in the DctP-TRAP SBPs is the formation of a salt bridge between a highly conserved arginine and a carboxylate group in the substrate, suggesting that these transporters might have evolved specifically for uptake of diverse organic acids. Remarkably, two of the DctP-TRAP SBPs are clearly dimers and the potential impact of this on transporter function will be discussed. Other SBPs used in secondary transporters are structurally similar to ABC SBPs, demonstrating that multiple families of SBPs have evolved to function with secondary transporters.

AB - Substrate-binding protein (SBP)-dependent secondary transporters are ubiquitous in prokaryotes yet poorly characterised. Recently, the structures of over 10 prokaryotic SBPs have been solved, which we compare here to consider their impact on our understanding of transporter function and evolution. Seven structures are from tripartite ATP-independent periplasmic (TRAP) transporters of the DctP-type, which have similar overall structures distinct from SBPs used by ATP-binding cassette (ABC) transporters, despite recognising a range of substrates. A defining feature of substrate recognition in the DctP-TRAP SBPs is the formation of a salt bridge between a highly conserved arginine and a carboxylate group in the substrate, suggesting that these transporters might have evolved specifically for uptake of diverse organic acids. Remarkably, two of the DctP-TRAP SBPs are clearly dimers and the potential impact of this on transporter function will be discussed. Other SBPs used in secondary transporters are structurally similar to ABC SBPs, demonstrating that multiple families of SBPs have evolved to function with secondary transporters.

KW - EXTRACYTOPLASMIC-SOLUTE-RECEPTOR

KW - HAEMOPHILUS-INFLUENZAE

KW - CRYSTAL-STRUCTURE

KW - ACID-BINDING

KW - SALMONELLA-TYPHIMURIUM

KW - HALOMONAS-ELONGATA

KW - THERMUS-THERMOPHILUS

KW - STRUCTURAL-ANALYSIS

KW - CITRATE TRANSPORT

KW - ABC TRANSPORTER

UR - http://www.scopus.com/inward/record.url?scp=77956987102&partnerID=8YFLogxK

U2 - 10.1016/j.tim.2010.06.009

DO - 10.1016/j.tim.2010.06.009

M3 - Review article

C2 - 20656493

SN - 0966-842X

VL - 18

SP - 471

EP - 478

JO - Trends in microbiology

JF - Trends in microbiology

IS - 10

ER -