Computational modelling of H+-coupled peptide transport via human PEPT1

H + -coupled peptide transporter 1 (PEPT1) mediates the transport of small peptides and peptide-like drugs in a pH- and voltage-dependent manner. Here, we investigated the transport mechanisms of PEPT1 for neutral and charged substrates by experimental studies and computational simulation. Uptake st...

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Bibliographic Details
Published in:The Journal of physiology 2005-06, Vol.565 (2), p.429-439
Main Authors: Irie, Megumi, Terada, Tomohiro, Katsura, Toshiya, Matsuoka, Satoshi, Inui, Ken‐ichi
Format: Article
Language:English
Subjects:
Anions - metabolism
Caco-2 Cells
Cations - metabolism
Cephalosporins - pharmacokinetics
Computer Simulation
Dipeptides - pharmacokinetics
Electrochemistry
Humans
Hydrogen-Ion Concentration
Membrane Potentials - physiology
Models, Chemical
Molecular and Genomic Physiology
Peptide Transporter 1
Peptides - metabolism
Protein Binding
Protons
Symporters - chemistry
Symporters - metabolism
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Summary:H + -coupled peptide transporter 1 (PEPT1) mediates the transport of small peptides and peptide-like drugs in a pH- and voltage-dependent manner. Here, we investigated the transport mechanisms of PEPT1 for neutral and charged substrates by experimental studies and computational simulation. Uptake studies revealed that the Michaelis-Menten constant ( K m ) of glycylsarcosine (Gly-Sar), a neutral substrate, decreased with a fall in pH from 7.4 to 5.5, but at pH 5.0, the K m increased again. In contrast, the K m value of an anionic substrate, ceftibuten, declined steadily with decreasing pH. Based on these findings and information from the literature, we hypothesized the transport mechanisms in which (1) H + binds to not only the H + -binding site, but also the substrate-binding site; and (2) H + at the substrate-binding site inhibits the interaction of neutral and cationic substrates, but is necessary for that of anionic substrates. To validate these hypotheses, a computational model was constructed and various properties of substrate transport by PEPT1 were simulated. Our model reproduced the voltage dependence, hyperbolic saturation and bell-shaped pH-profile of Gly-Sar transport. Moreover, the various transport properties of negatively and positively charged substrates were also reconstructed. These findings indicated that the inferred mechanisms are able to sufficiently interpret the transport of both neutral and charged substrates by PEPT1.
ISSN:0022-3751
1469-7793
DOI:10.1113/jphysiol.2005.084582