title: Crystal Structures of the Extracellular Domain from PepT1 and PepT2 Provide Novel Insights into Mammalian Peptide Transport.
abstract: Mammals obtain nitrogen via the uptake of di- and tri-peptides in the gastrointestinal tract through the action of PepT1 and PepT2, which are members of the POT family of proton-coupled oligopeptide transporters. PepT1 and PepT2 also play an important role in drug transport in the human body. Recent crystal structures of bacterial homologs revealed a conserved peptide-binding site and mechanism of transport. However, a key structural difference exists between bacterial and mammalian homologs with only the latter containing a large extracellular domain, the function of which is currently unknown. Here, we present the crystal structure of the extracellular domain from both PepT1 and PepT2 that reveal two immunoglobulin-like folds connected in tandem, providing structural insight into mammalian peptide transport. Functional and biophysical studies demonstrate that these domains interact with the intestinal protease trypsin, suggesting a role in clustering proteolytic activity to the site of peptide transport in eukaryotic cells.
authors: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
authors: John H
authors: JH
authors: Beale
authors: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
authors: Joanne L
authors: JL
authors: Parker
authors: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
authors: Firdaus
authors: F
authors: Samsudin
authors: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK.
authors: Anne L
authors: AL
authors: Barrett
authors: Department of Biological Sciences, Oxford Brookes University, Oxford OX3 0BP, UK.
authors: Anish
authors: A
authors: Senan
authors: Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, UK; OPPF-UK, Research Complex at Harwell, Harwell Oxford, Didcot, Oxfordshire OX11 0FA, UK.
authors: Louise E
authors: LE
authors: Bird
authors: Research Complex at Harwell, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0FA, UK; ISIS Spallation Neutron and Muon Source, Rutherford Appleton Laboratory, Oxfordshire OX11 0FA, UK; School of Biosciences, School of Biosciences, Sutton Bonington Campus, Leicestershire LE12 5RD, UK.
authors: David
authors: D
authors: Scott
authors: Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, UK; OPPF-UK, Research Complex at Harwell, Harwell Oxford, Didcot, Oxfordshire OX11 0FA, UK.
authors: Raymond J
authors: RJ
authors: Owens
authors: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; OXION Initiative in Ion Channels and Membrane Transport, University of Oxford OX1 3PU, UK.
authors: Mark S P
authors: MSP
authors: Sansom
authors: Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK; OXION Initiative in Ion Channels and Membrane Transport, University of Oxford OX1 3PU, UK.
authors: Stephen J
authors: SJ
authors: Tucker
authors: Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, UK.
authors: David
authors: D
authors: Meredith
authors: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
authors: Philip W
authors: PW
authors: Fowler
authors: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; OXION Initiative in Ion Channels and Membrane Transport, University of Oxford OX1 3PU, UK. Electronic address: simon.newstead@bioch.ox.ac.uk.
authors: Simon
authors: S
authors: Newstead
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007700:Kinetics; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D000074011:Peptide Transporter 1; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D027981:Symporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014357:Trypsin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D009842:Oligopeptides; D000074011:Peptide Transporter 1; D011994:Recombinant Proteins; C489941:Slc15a1 protein, mouse; D027981:Symporters; C093694:hydrogen-coupled oligopeptide transporter PepT2; D014357:Trypsin