A novel NAD-binding protein revealed by the crystal structure of 2,3-diketo-L-gulonate reductase (YiaK).
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Forouhar F, Lee I, Benach J, Kulkarni K, Xiao R, Acton TB, Montelione GT, Tong L
A novel NAD-binding protein revealed by the crystal structure of 2,3-diketo-L-gulonate reductase (YiaK).
J Biol Chem. 2004 Mar 26;279(13):13148-55. Epub 2004 Jan 12.
- PubMed ID
- 14718529 [ View in 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.