A Novel NAD-binding Protein Revealed by the Crystal Structure of 2,3-Diketo-L-gulonate Reductase (YiaK).Forouhar, F., Lee, I., Benach, J., Kulkarni, K., Xiao, R., Acton, T.B., Montelione, G.T., Tong, L.
(2004) J Biol Chem 279: 13148-13155
- PubMed: 14718529
- DOI: https://doi.org/10.1074/jbc.M313580200
- Primary Citation of Related Structures:
- PubMed 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.
Department of Biological Sciences, Northeast Structural Genomics Consortium, Columbia University, New York, NY 10027, USA.