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PDBsum entry 4d1b
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Transport protein
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PDB id
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4d1b
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References listed in PDB file
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Key reference
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Title
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Molecular mechanism of ligand recognition by membrane transport protein, Mhp1.
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Authors
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K.J.Simmons,
S.M.Jackson,
F.Brueckner,
S.G.Patching,
O.Beckstein,
E.Ivanova,
T.Geng,
S.Weyand,
D.Drew,
J.Lanigan,
D.J.Sharples,
M.S.Sansom,
S.Iwata,
C.W.Fishwick,
A.P.Johnson,
A.D.Cameron,
P.J.Henderson.
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Ref.
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Embo J, 2014,
33,
1831-1844.
[DOI no: ]
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PubMed id
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Abstract
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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.
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