1DXY

STRUCTURE OF D-2-HYDROXYISOCAPROATE DEHYDROGENASE

Summary for 1DXY

• Entry DOI: 10.2210/pdb1dxy/pdb
• Descriptor: D-2-HYDROXYISOCAPROATE DEHYDROGENASE, SULFATE ION, NICOTINAMIDE-ADENINE-DINUCLEOTIDE, ... (5 entities in total)
• Functional Keywords: d-2-hydroxycarboxylate dehydrogenase, d-lactate dehydrogenase, oxidoreductase
• Biological source: Lactobacillus casei
• Total number of polymer chains: 1
• Total formula weight: 37915.53

Authors

Dengler, U.,Niefind, K.,Kiess, M.,Schomburg, D. (deposition date: 1996-08-13, release date: 1997-06-16, Last modification date: 2024-05-22)

Primary citation

Dengler, U.,Niefind, K.,Kiess, M.,Schomburg, D.
Crystal structure of a ternary complex of D-2-hydroxyisocaproate dehydrogenase from Lactobacillus casei, NAD+ and 2-oxoisocaproate at 1.9 A resolution.
J.Mol.Biol., 267:640-660, 1997

PubMed Abstract: D-2-hydroxyisocaproate dehydrogenase (D-HicDH) from Lactobacillus casei is a homodimer with 333 amino acids and a molecular mass of 37 kDa per subunit. The enzyme belongs to the protein family of NAD+-dependent D-2-hydroxycarboxylate dehydrogenases and within this family to the subgroup of D-lactate dehydrogenases (D-LDHs). Compared with other D-LDHs D-HicDH is characterized by a very low specificity regarding size and chemical constitution of the accepted D-2-hydroxycarboxylates. Hexagonal crystals of recombinant D-HicDH in the presence of NAD+ and 2-oxoisocaproate (4-methyl-2-oxopentanoate) were grown with ammonium sulphate as precipitating agent. The structure of these crystals was solved by molecular replacement and refined to a final R-factor of 19.6% for all measured X-ray reflections in the resolution range (infinity to 1.86 A). Both NAD+ and 2-oxoisocaproate were identified in the electron density map; binding of the latter in the active site, however, competes with a sulphate ion, which is also defined by electron density. Additionally the final model contains 182 water molecules and a second sulphate ion. The binding of both an in vitro substrate and the natural cosubstrate in the active site provides substantial insight into the catalytic mechanism and allows us to assess previously published active site models for this enzyme family, in particular the two most controversial points, the role of the conserved Arg234 and substrate binding. Furthermore the overall topology and details of the D-HicDH structure are described, discussed against the background of homologous structures and compared with one closely and one distantly related protein.

PubMed: 9126843
DOI: 10.1006/jmbi.1996.0864

Experimental method

X-RAY DIFFRACTION (1.86 Å)