1AXG

CRYSTAL STRUCTURE OF THE VAL203->ALA MUTANT OF LIVER ALCOHOL DEHYDROGENASE COMPLEXED WITH COFACTOR NAD AND INHIBITOR TRIFLUOROETHANOL SOLVED TO 2.5 ANGSTROM RESOLUTION

Summary for 1AXG

• Entry DOI: 10.2210/pdb1axg/pdb
• Descriptor: ALCOHOL DEHYDROGENASE, ZINC ION, NICOTINAMIDE-ADENINE-DINUCLEOTIDE, ... (5 entities in total)
• Functional Keywords: oxidoreductase (nad(a)-choh(d)), alcohol dehydrogenase, oxidoreductase
• Biological source: Equus caballus (horse)
• Cellular location: Cytoplasm: P00327
• Total number of polymer chains: 4
• Total formula weight: 162878.02

Authors

Colby, T.D.,Chin, J.K.,Bahnson, B.J.,Goldstein, B.M.,Klinman, J.P. (deposition date: 1997-10-15, release date: 1998-04-15, Last modification date: 2024-10-30)

Primary citation

Bahnson, B.J.,Colby, T.D.,Chin, J.K.,Goldstein, B.M.,Klinman, J.P.
A link between protein structure and enzyme catalyzed hydrogen tunneling.
Proc.Natl.Acad.Sci.USA, 94:12797-12802, 1997

PubMed Abstract: We present evidence that the size of an active site side chain may modulate the degree of hydrogen tunneling in an enzyme-catalyzed reaction. Primary and secondary kH/kT and kD/kT kinetic isotope effects have been measured for the oxidation of benzyl alcohol catalyzed by horse liver alcohol dehydrogenase at 25 degrees C. As reported in earlier studies, the relationship between secondary kH/kT and kD/kT isotope effects provides a sensitive probe for deviations from classical behavior. In the present work, catalytic efficiency and the extent of hydrogen tunneling have been correlated for the alcohol dehydrogenase-catalyzed hydride transfer among a group of site-directed mutants at position 203. Val-203 interacts with the opposite face of the cofactor NAD+ from the alcohol substrate. The reduction in size of this residue is correlated with diminished tunneling and a two orders of magnitude decrease in catalytic efficiency. Comparison of the x-ray crystal structures of a ternary complex of a high-tunneling (Phe-93 --> Trp) and a low-tunneling (Val-203 --> Ala) mutant provides a structural basis for the observed effects, demonstrating an increase in the hydrogen transfer distance for the low-tunneling mutant. The Val-203 --> Ala ternary complex crystal structure also shows a hyperclosed interdomain geometry relative to the wild-type and the Phe-93 --> Trp mutant ternary complex structures. This demonstrates a flexibility in interdomain movement that could potentially narrow the distance between the donor and acceptor carbons in the native enzyme and may enhance the role of tunneling in the hydride transfer reaction.

PubMed: 9371755
DOI: 10.1073/pnas.94.24.12797

Experimental method

X-RAY DIFFRACTION (2.5 Å)