title: The 2.9A resolution crystal structure of malate dehydrogenase from Archaeoglobus fulgidus: mechanisms of oligomerisation and thermal stabilisation.
abstract: The crystal structure of malate dehydrogenase from the hyperthermophilic archaeon Archeoglobus fulgidus, in complex with its cofactor NAD, was solved at 2.9A resolution. The crystal structure shows a compact homodimer with one coenzyme bound per subunit. The substrate binding site is occupied by a sulphate ion. In order to gain insight into adaptation mechanisms, which allow the protein to be stable and active at high temperatures, the 3D structure was compared to those of several thermostable and hyperthermostable homologues, and to halophilic malate dehydrogenase. The hyperthermostable A. fulgidus MalDH protein displays a reduction of the solvent-exposed surface, an optimised compact hydrophobic core, a high number of hydrogen bonds, and includes a large number of ion pairs at the protein surface. These features occur concomitantly with a reduced number of residues in the protein subunit, due to several deletions in loop regions. The loops are further stiffened by ion pair links with secondary structure elements. A. fulgidus malate dehydrogenase is the only dimeric protein known to date that belongs to the [LDH-like] MalDH family. All the other known members of this family are homo-tetramers. The crystal structures revealed that the association of the dimers to form tetramers is prevented by several deletions, taking place at the level of two loops that are known to be essential for the tetramerisation process within the LDH and [LDH-like] MalDH enzymes.
authors.affiliation: Laboratoire de Biophysique Moléculaire, Institut de Biologie Structurale J.-P. Ebel CEA CNRS UJF, UMR-5075, 41 rue Jules Horowitz, 38027 Cedex 01, Grenoble, France.
authors.forename: Adriana
authors.initials: A
authors.lastname: Irimia
authors.forename: Frédéric M D
authors.initials: FM
authors.lastname: Vellieux
authors.forename: Dominique
authors.initials: D
authors.lastname: Madern
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Zaccaï
authors.forename: Andrey
authors.initials: A
authors.lastname: Karshikoff
authors.forename: Gudrun
authors.initials: G
authors.lastname: Tibbelin
authors.forename: Rudolf
authors.initials: R
authors.lastname: Ladenstein
authors.forename: Torleiv
authors.initials: T
authors.lastname: Lien
authors.forename: Nils Kåre
authors.initials: NK
authors.lastname: Birkeland
mesh_terms: D019611:Archaeoglobus fulgidus / Q000201:enzymology*; D018360:Crystallography, X-Ray; D019281:Dimerization; D004795:Enzyme Stability; D008291:Malate Dehydrogenase / Q000737:chemistry*; D015394:Molecular Structure; D009243:NAD / Q000737:chemistry; D011487:Protein Conformation; D040681:Structural Homology, Protein; D013696:Temperature
chemical_list: D009243:NAD; D008291:Malate Dehydrogenase