title: A novel NAD-binding protein revealed by the crystal structure of 2,3-diketo-L-gulonate reductase (YiaK).
abstract: Escherichia coli YiaK catalyzes the reduction of 2,3-diketo-L-gulonate in the presence of NADH. It belongs to a large family of oxidoreductases that is conserved in archaea, bacteria, and eukaryotes but shows no sequence homology to other proteins. We report here the crystal structures at up to 2.0-A resolution of YiaK alone and in complex with NAD-tartrate. YiaK has a new polypeptide backbone fold and a novel mode of recognizing the NAD cofactor. In addition, NAD is bound in an unusual conformation, at the interface of a dimer of the enzyme. The crystallographic analysis unexpectedly revealed the binding of tartrate in the active site. Enzyme kinetics studies confirm that tartrate and the related D-malate are inhibitors of YiaK. In contrast to most other enzymes where substrate binding produces a more closed conformation, the binding of NAD-tartrate to YiaK produces a more open active site. The free enzyme conformation is incompatible with NAD binding. His(44) is likely the catalytic residue of the enzyme.
authors.affiliation: Department of Biological Sciences, Northeast Structural Genomics Consortium, Columbia University, New York, NY 10027, USA.
authors.forename: Farhad
authors.initials: F
authors.lastname: Forouhar
authors.forename: Insun
authors.initials: I
authors.lastname: Lee
authors.forename: Jordi
authors.initials: J
authors.lastname: Benach
authors.forename: Kaushal
authors.initials: K
authors.lastname: Kulkarni
authors.forename: Rong
authors.initials: R
authors.lastname: Xiao
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Acton
authors.forename: Gaetano T
authors.initials: GT
authors.lastname: Montelione
authors.forename: Liang
authors.initials: L
authors.lastname: Tong
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D019281:Dimerization; D004583:Electrons; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009243:NAD / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013400:Sugar Acids / Q000737:chemistry*; D013401:Sugar Alcohol Dehydrogenases / Q000737:chemistry* / Q000378:metabolism; D013644:Tartrates / Q000737:chemistry
chemical_list: D029968:Escherichia coli Proteins; D013400:Sugar Acids; D013644:Tartrates; D009243:NAD; C015252:gulonic acid; D013401:Sugar Alcohol Dehydrogenases; C484696:2,3-diketo-L-gulonate reductase; C029768:tartaric acid