title: Crystal structure of archaeal highly thermostable L-aspartate dehydrogenase/NAD/citrate ternary complex.
abstract: The crystal structure of the highly thermostable L-aspartate dehydrogenase (L-aspDH; EC 1.4.1.21) from the hyperthermophilic archaeon Archaeoglobus fulgidus was determined in the presence of NAD and a substrate analog, citrate. The dimeric structure of A. fulgidus L-aspDH was refined at a resolution of 1.9 A with a crystallographic R-factor of 21.7% (R(free) = 22.6%). The structure indicates that each subunit consists of two domains separated by a deep cleft containing an active site. Structural comparison of the A. fulgidus L-aspDH/NAD/citrate ternary complex and the Thermotoga maritima L-aspDH/NAD binary complex showed that A. fulgidus L-aspDH assumes a closed conformation and that a large movement of the two loops takes place during substrate binding. Like T. maritima L-aspDH, the A. fulgidus enzyme is highly thermostable. But whereas a large number of inter- and intrasubunit ion pairs are responsible for the stability of A. fulgidus L-aspDH, a large number of inter- and intrasubunit aromatic pairs stabilize the T. maritima enzyme. Thus stabilization of these two L-aspDHs appears to be achieved in different ways. This is the first detailed description of substrate and coenzyme binding to L-aspDH and of the molecular basis of the high thermostability of a hyperthermophilic L-aspDH.
authors.affiliation: Institute of Genetic Resources, Faculty of Agriculture, Kyushu University, Fukuoka, Japan.
authors.forename: Kazunari
authors.initials: K
authors.lastname: Yoneda
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Sakuraba
authors.forename: Hideaki
authors.initials: H
authors.lastname: Tsuge
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Katunuma
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Ohshima
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019611:Archaeoglobus fulgidus / Q000201:enzymology*; D001224:Aspartic Acid / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D019343:Citric Acid / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D004795:Enzyme Stability; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009243:NAD / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013816:Thermodynamics
chemical_list: D019843:Archaeal Proteins; D009243:NAD; D019343:Citric Acid; D001224:Aspartic Acid; D000594:Amino Acid Oxidoreductases; C025745:aspartate dehydrogenase