title: Influence of an anion-binding site in the stabilization of halophilic malate dehydrogenase from Haloarcula marismortui.
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.
authors: 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
authors: Dominique
authors: D
authors: Madern
authors: Christine
authors: C
authors: Ebel
mesh_terms: D000838:Anions / Q000378:metabolism; D001665:Binding Sites / Q000187:drug effects; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D005459:Fluorides / Q000494:pharmacology; D019614:Haloarcula marismortui / Q000201:enzymology*; D008291:Malate Dehydrogenase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D009154:Mutation; D011189:Potassium Chloride / Q000494:pharmacology; D017680:Potassium Compounds / Q000494:pharmacology; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D000838:Anions; D017680:Potassium Compounds; D021122:Protein Subunits; D011189:Potassium Chloride; C033320:potassium fluoride; D008291:Malate Dehydrogenase; D005459:Fluorides