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Molecular mechanism of ligand recognition by membrane transport protein, Mhp1
Author(s) -
Simmons Katie J,
Jackson Scott M,
Brueckner Florian,
Patching Simon G,
Beckstein Oliver,
Ivanova Ekaterina,
Geng Tian,
Weyand Simone,
Drew David,
Lanigan Joseph,
Sharples David J,
Sansom Mark SP,
Iwata So,
Fishwick Colin WG,
Johnson A Peter,
Cameron Alexander D,
Henderson Peter JF
Publication year - 2014
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.15252/embj.201387557
Subject(s) - hydantoin , biology , major facilitator superfamily , stereochemistry , symporter , biochemistry , transporter , chemistry , gene
The hydantoin transporter Mhp1 is a sodium‐coupled secondary active transport protein of the nucleobase‐cation‐symport family and a member of the widespread 5‐helix inverted repeat superfamily of transporters. The structure of Mhp1 was previously solved in three different conformations providing insight into the molecular basis of the alternating access mechanism. Here, we elucidate detailed events of substrate binding, through a combination of crystallography, molecular dynamics, site‐directed mutagenesis, biochemical/biophysical assays, and the design and synthesis of novel ligands. We show precisely where 5‐substituted hydantoin substrates bind in an extended configuration at the interface of the bundle and hash domains. They are recognised through hydrogen bonds to the hydantoin moiety and the complementarity of the 5‐substituent for a hydrophobic pocket in the protein. Furthermore, we describe a novel structure of an intermediate state of the protein with the external thin gate locked open by an inhibitor, 5‐(2‐naphthylmethyl)‐L‐hydantoin, which becomes a substrate when leucine 363 is changed to an alanine. We deduce the molecular events that underlie acquisition and transport of a ligand by Mhp1.