Crystal structure of a prokaryotic homologue of the mammalian oligopeptide-proton symporters, PepT1 and PepT2.
PepT1 and PepT2 are major facilitator superfamily (MFS) transporters that utilize a proton gradient to drive the uptake of di- and tri-peptides in the small intestine and kidney, respectively. They are the major routes by which we absorb dietary nitrogen and many orally administered drugs. Here, we present the crystal structure of PepT(So), a functionally similar prokaryotic homologue of the mammalian peptide transporters from Shewanella oneidensis. This structure, refined using data up to 3.6 Å resolution, reveals a ligand-bound occluded state for the MFS and provides new insights into a general transport mechanism. We have located the peptide-binding site in a central hydrophilic cavity, which occludes a bound ligand from both sides of the membrane. Residues thought to be involved in proton coupling have also been identified near the extracellular gate of the cavity. Based on these findings and associated kinetic data, we propose that PepT(So) represents a sound model system for understanding mammalian peptide transport as catalysed by PepT1 and PepT2.
Division of Molecular Biosciences, Membrane Protein Crystallography Group, Imperial College London, London, UK. simon.newstead@bioch.ox.ac.uk
Simon
S
Newstead
David
D
Drew
Alexander D
AD
Cameron
Vincent L G
VL
Postis
Xiaobing
X
Xia
Philip W
PW
Fowler
Jean C
JC
Ingram
Elisabeth P
EP
Carpenter
Mark S P
MS
Sansom
Michael J
MJ
McPherson
Stephen A
SA
Baldwin
So
S
Iwata
D001665:Binding Sites / Q000235:genetics; D003461:Crystallography; D008958:Models, Molecular; D000074011:Peptide Transporter 1; D020592:Shewanella / Q000235:genetics*; D027981:Symporters / Q000235:genetics / Q000648:ultrastructure*
D000074011:Peptide Transporter 1; D027981:Symporters; C093694:hydrogen-coupled oligopeptide transporter PepT2