title: Unusual folded conformation of nicotinamide adenine dinucleotide bound to flavin reductase P.
abstract: The 2.1 A resolution crystal structure of flavin reductase P with the inhibitor nicotinamide adenine dinucleotide (NAD) bound in the active site has been determined. NAD adopts a novel, folded conformation in which the nicotinamide and adenine rings stack in parallel with an inter-ring distance of 3.6 A. The pyrophosphate binds next to the flavin cofactor isoalloxazine, while the stacked nicotinamide/adenine moiety faces away from the flavin. The observed NAD conformation is quite different from the extended conformations observed in other enzyme/NAD(P) structures; however, it resembles the conformation proposed for NAD in solution. The flavin reductase P/NAD structure provides new information about the conformational diversity of NAD, which is important for understanding catalysis. This structure offers the first crystallographic evidence of a folded NAD with ring stacking, and it is the first enzyme structure containing an FMN cofactor interacting with NAD(P). Analysis of the structure suggests a possible dynamic mechanism underlying NADPH substrate specificity and product release that involves unfolding and folding of NADP(H).
authors.affiliation: Department of Chemistry, University of Missouri-Columbia 65211, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Tanner
authors.forename: S C
authors.initials: SC
authors.lastname: Tu
authors.forename: L J
authors.initials: LJ
authors.lastname: Barbour
authors.forename: C L
authors.initials: CL
authors.lastname: Barnes
authors.forename: K L
authors.initials: KL
authors.lastname: Krause
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D019281:Dimerization; D038181:FMN Reductase; D016018:Least-Squares Analysis; D046911:Macromolecular Substances; D008958:Models, Molecular; D009243:NAD / Q000737:chemistry* / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D014733:Vibrio / Q000201:enzymology
chemical_list: D046911:Macromolecular Substances; D009243:NAD; D038181:FMN Reductase; D009247:NADH, NADPH Oxidoreductases