tailieunhanh - Báo cáo khoa học: Crystal structure of archaeal highly thermostable L-aspartate dehydrogenase/NAD/citrate ternary complex

The crystal structure of the highly thermostablel-aspartate dehydrogenase (l-aspDH; EC ) from the hyperthermophilic archaeon Archaeoglo-bus fulgiduswas determined in the presence of NAD and a substrate ana-log, citrate. The dimeric structure of A. fulgidusl-aspDH was refined at a resolution of A ˚ with a crystallographicR-factor of (Rfree ¼ ). | ỊFEBS Journal Crystal structure of archaeal highly thermostable L-aspartate dehydrogenase NAD citrate ternary complex Kazunari Yoneda1 Haruhiko Sakuraba2 Hideaki Tsuge3 Nobuhiko Katunuma3 and Toshihisa Ohshima1 1 Institute of Genetic Resources Faculty of Agriculture Kyushu University Fukuoka Japan 2 Department of BiologicalScience and Technology Faculty of Engineering The University of Tokushima Japan 3 Institute for Health Sciences Tokushima Bunri University Japan Keywords aromatic pair interaction hyperthermostable L-aspartate dehydrogenase ion-pair interaction NAD biosynthesis Correspondence T. Ohshima Institute of Genetic Resources Faculty of Agriculture Kyushu University Hakozaki Fukuoka 812-8581 Japan Fax 81 92 642 3059 Tel 81 92 642 3053 E-mail ohshima@ Received 13 May 2007 revised 26 June 2007 accepted 28 June 2007 doi The crystal structure of the highly thermostable L-aspartate dehydrogenase L-aspDH EC from the hyperthermophilic archaeon Archaeoglo-bus 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 A with a crystallographic R-factor of Rfree . The structure indicates that each subunit consists of two domains separated by a deep cleft containing an active site. Structural comparison of the 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 .