1n8k

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Revision as of 19:55, 20 November 2007

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spinqualitylabelsall models 1n8k, resolution 1.13Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Horse Liver Alcohol Dehydrogenase Val292Thr Mutant Complexed to NAD+ and Pyrazole

Overview

Amino acid residues Thr-178, Val-203, and Val-292, which interact with the, nicotinamide ring of the coenzyme bound to alcohol dehydrogenase (ADH), may facilitate hydride transfer and hydrogen tunneling by orientation and, dynamic effects. The T178S, T178V, V203A, V292A, V292S, and V292T, substitutions significantly alter the steady state and transient kinetics, of the enzyme. The V292A, V292S, and V292T enzymes have decreased affinity, for coenzyme (NAD+ by 30-50-fold and NADH by 35-75-fold) as compared to, the wild-type enzyme. The substitutions in the nicotinamide binding site, decrease the rate constant of hydride transfer for benzyl alcohol, oxidation by 3-fold (for V292T ADH) to 16-fold (for V203A ADH). The modest, effects suggest that catalysis does not depend critically on individual, residues and that several residues in the nicotinamide binding site, contribute to catalysis. The structures of the V292T ADH-NAD+-pyrazole and, wild-type ADH-NAD+-4-iodopyrazole ternary complexes are very similar. Only, subtle changes in the V292T enzyme cause the large changes in coenzyme, binding and the small change in hydride transfer. In these complexes, one, pyrazole nitrogen binds to the catalytic zinc, and the other nitrogen, forms a partial covalent bond with C4 of the nicotinamide ring, which, adopts a boat conformation that is postulated to be relevant for hydride, transfer. The results provide an experimental basis for evaluating the, contributions of dynamics to hydride transfer.

About this Structure

1N8K is a Single protein structure of sequence from Equus caballus with ZN, NAJ, PZO and MPD as ligands. Active as Alcohol dehydrogenase, with EC number 1.1.1.1 Full crystallographic information is available from OCA.

Reference

Amino acid residues in the nicotinamide binding site contribute to catalysis by horse liver alcohol dehydrogenase., Rubach JK, Plapp BV, Biochemistry. 2003 Mar 18;42(10):2907-15. PMID:12627956

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