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PDBsum entry 2idv
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Translation regulator
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PDB id
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2idv
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References listed in PDB file
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Key reference
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Title
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The structure of eukaryotic translation initiation factor-4e from wheat reveals a novel disulfide bond.
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Authors
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A.F.Monzingo,
S.Dhaliwal,
A.Dutt-Chaudhuri,
A.Lyon,
J.H.Sadow,
D.W.Hoffman,
J.D.Robertus,
K.S.Browning.
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Ref.
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Plant Physiol, 2007,
143,
1504-1518.
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PubMed id
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Abstract
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Eukaryotic translation initiation factor-4E (eIF4E) recognizes and binds the
m(7) guanosine nucleotide at the 5' end of eukaryotic messenger RNAs; this
protein-RNA interaction is an essential step in the initiation of protein
synthesis. The structure of eIF4E from wheat (Triticum aestivum) was
investigated using a combination of x-ray crystallography and nuclear magnetic
resonance (NMR) methods. The overall fold of the crystallized protein was
similar to eIF4E from other species, with eight beta-strands, three
alpha-helices, and three extended loops. Surprisingly, the wild-type protein did
not crystallize with m(7)GTP in its binding site, despite the ligand being
present in solution; conformational changes in the cap-binding loops created a
large cavity at the usual cap-binding site. The eIF4E crystallized in a dimeric
form with one of the cap-binding loops of one monomer inserted into the cavity
of the other. The protein also contained an intramolecular disulfide bridge
between two cysteines (Cys) that are conserved only in plants. A Cys-to-serine
mutant of wheat eIF4E, which lacked the ability to form the disulfide,
crystallized with m(7)GDP in its binding pocket, with a structure similar to
that of the eIF4E-cap complex of other species. NMR spectroscopy was used to
show that the Cys that form the disulfide in the crystal are reduced in solution
but can be induced to form the disulfide under oxidizing conditions. The
observation that the disulfide-forming Cys are conserved in plants raises the
possibility that their oxidation state may have a role in regulating protein
function. NMR provided evidence that in oxidized eIF4E, the loop that is open in
the ligand-free crystal dimer is relatively flexible in solution. An NMR-based
binding assay showed that the reduced wheat eIF4E, the oxidized form with the
disulfide, and the Cys-to-serine mutant protein each bind m(7)GTP in a similar
and labile manner, with dissociation rates in the range of 20 to 100 s(-1).
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