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| {{STRUCTURE_1ab6| PDB=1ab6 | SCENE= }} | | {{STRUCTURE_1ab6| PDB=1ab6 | SCENE= }} |
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| '''STRUCTURE OF CHEY MUTANT F14N, V86T'''
| | ===STRUCTURE OF CHEY MUTANT F14N, V86T=== |
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| ==Overview==
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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. | | The line below this paragraph, {{ABSTRACT_PUBMED_9761905}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 9761905 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_9761905}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Phosphorylation]] | | [[Category: Phosphorylation]] |
| [[Category: Sensory transduction]] | | [[Category: Sensory transduction]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 10:04:02 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 16:31:17 2008'' |