Influence of an anion-binding site in the stabilization of halophilic malate dehydrogenase from Haloarcula marismortui.
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.
Madern
Dominique
D
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
Ebel
Christine
C
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
D000838:Anions; D017680:Potassium Compounds; D021122:Protein Subunits; D011189:Potassium Chloride; C033320:potassium fluoride; D008291:Malate Dehydrogenase; D005459:Fluorides