1wyg

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Revision as of 03:37, 21 November 2007


1wyg, resolution 2.6Å

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Crystal Structure of a Rat Xanthine Dehydrogenase Triple Mutant (C535A, C992R and C1324S)

Overview

Mammalian xanthine dehydrogenase can be converted to xanthine oxidase by, modification of cysteine residues or by proteolysis of the enzyme, polypeptide chain. Here we present evidence that the Cys(535) and Cys(992), residues of rat liver enzyme are indeed involved in the rapid conversion, from the dehydrogenase to the oxidase. The purified mutants C535A and/or, C992R were significantly resistant to conversion by incubation with, 4,4'-dithiodipyridine, whereas the recombinant wild-type enzyme converted, readily to the oxidase type, indicating that these residues are, responsible for the rapid conversion. The C535A/C992R mutant, however, converted very slowly during prolonged incubation with, 4,4'-dithiodipyridine, and this slow conversion was blocked by the, addition of NADH, suggesting that another cysteine couple located near the, NAD(+) binding site is responsible for the slower conversion. On the other, hand, the C535A/C992R/C1316S and C535A/C992R/C1324S mutants were, completely resistant to conversion, even on prolonged incubation with, 4,4'-dithiodipyridine, indicating that Cys(1316) and Cys(1324) are, responsible for the slow conversion. The crystal structure of the, C535A/C992R/C1324S mutant was determined in its demolybdo form, confirming, its dehydrogenase conformation.

About this Structure

1WYG is a Single protein structure of sequence from Rattus norvegicus with PO4, CA, FES, FAD, SAL and ACY as ligands. Full crystallographic information is available from OCA.

Reference

Mechanism of the conversion of xanthine dehydrogenase to xanthine oxidase: identification of the two cysteine disulfide bonds and crystal structure of a non-convertible rat liver xanthine dehydrogenase mutant., Nishino T, Okamoto K, Kawaguchi Y, Hori H, Matsumura T, Eger BT, Pai EF, Nishino T, J Biol Chem. 2005 Jul 1;280(26):24888-94. Epub 2005 May 4. PMID:15878860

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