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PDBsum entry 1ab5
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Structure analysis of two chey mutants: importance of the hydrogen-Bond contribution to protein stability.
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Authors
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D.Wilcock,
M.T.Pisabarro,
E.López-Hernandez,
L.Serrano,
M.Coll.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 1998,
54,
378-385.
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PubMed id
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Note In the PDB file this reference is
annotated as "TO BE PUBLISHED".
The citation details given above were identified by an automated
search of PubMed on title and author
names, giving a
percentage match of
0%.
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Abstract
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The crystal structures of two double mutants (F14N/V21T and F14N/V86T) of the
signal transduction protein CheY have been determined to a resolution of 2.4 and
2.2 A, respectively. The structures were solved by molecular replacement and
refined to final R values of 18.4 and 19.2%, respectively. Together with
urea-denaturation experiments the structures have been used to analyse the
effects of mutations where hydrophobic residues are replaced by residues capable
of establishing hydrogen bonds. The large increase in stabilization (-12.1 kJ
mol-1) of the mutation Phe14Asn arises from two factors: a reverse hydrophobic
effect and the formation of a good N-cap at alpha-helix 1. In addition, a
forward-backward hydrogen-bonding pattern, resembling an N-capping box and
involving Asn14 and Arg18, has been found. The two Val to Thr mutations at the
hydrophobic core have different thermodynamic effects: the mutation Val21Thr
does not affect the stability of the protein while the mutation Val86Thr causes
a small destabilization of 1.7 kJ mol-1. At site 21 a backward side
chain-to-backbone hydrogen bond is formed inside alpha-helix 1 with the carbonyl
O atom of the i - 4 residue without movement of the mutated side chain. The
destabilizing effect of introducing a polar group in the core is efficiently
compensated for by the formation of an extra hydrogen bond. At site 86 the new
Ogamma atom escapes from the hydrophobic environment by a chi1 rotation into an
adjacent hydrophilic cavity to form a new hydrogen bond. In this case the
isosteric Val to Thr substitution is disruptive but the loss in stabilization
energy is partly compensated by the formation of a hydrogen bond. The two
crystal structures described in this work underline the significance of the
hydrogen-bond component to protein stability.
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