Influence of an anion-binding site in the stabilization of halophilic malate dehydrogenase from Haloarcula marismortui |
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Authors: | Madern Dominique Ebel Christine |
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Institution: | Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075, CEA, CNRS, Université Joseph Fourier, 41 rue Jules Horowitz, F-38027 Grenoble, France. madern@ibs.fr |
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Abstract: | Halophilic proteins have evolved to be soluble, stable and active in high salt concentration. Crystallographic studies have shown that surface enrichment by acidic amino acids is a common structural feature of halophilic proteins. In addition, ion-binding sites have also been observed in most of the cases. The role of chloride-binding sites in halophilic adaptation was addressed in a site-directed mutagenesis study of tetrameric malate dehydrogenase from Haloarcula marismortui. The mutation of K 205, which is involved in an inter-subunit chloride-binding site, drastically modified the enzyme stability in the presence of KCl, but not in the presence of KF. The oligomeric state of the K205A] mutant changes with the nature of the anion. At high salt concentration, the K205A] mutant is a dimer when the anion is a chloride ion, whereas it is a tetramer when the fluoride ion is used. The results highlight the role of anion-binding sites in protein adaptation to high salt conditions. |
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Keywords: | Halophilic Ion binding Malate dehydrogenase Protein solvent Stability |
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