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Titolo:
STRUCTURAL CHARACTERIZATION OF THE ZINC SITE IN ESCHERICHIA-COLI L-THREONINE DEHYDROGENASE USING EXTENDED X-RAY-ABSORPTION FINE-STRUCTURE SPECTROSCOPY
Autore:
CLARKBALDWIN K; JOHNSON AR; CHEN YW; DEKKER EE; PENNERHAHN JE;
Indirizzi:
UNIV MICHIGAN,DEPT CHEM ANN ARBOR MI 48109 UNIV MICHIGAN,DEPT CHEM ANN ARBOR MI 48109 UNIV MICHIGAN,DEPT BIOL CHEM ANN ARBOR MI 48109
Titolo Testata:
Inorganica Chimica Acta
fascicolo: 1-2, volume: 276, anno: 1998,
pagine: 215 - 221
SICI:
0020-1693(1998)276:1-2<215:SCOTZS>2.0.ZU;2-E
Fonte:
ISI
Lingua:
ENG
Soggetto:
LIVER ALCOHOL-DEHYDROGENASE; SORBITOL DEHYDROGENASE; CARBOXYL GROUPS; GENE; PURIFICATION; ENZYME; ACTIVATION; CYSTEINE; FAMILY; K-12;
Keywords:
EXAFS; ZINC SITE; L-THREONINE DEHYDROGENASE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
44
Recensione:
Indirizzi per estratti:
Citazione:
K. Clarkbaldwin et al., "STRUCTURAL CHARACTERIZATION OF THE ZINC SITE IN ESCHERICHIA-COLI L-THREONINE DEHYDROGENASE USING EXTENDED X-RAY-ABSORPTION FINE-STRUCTURE SPECTROSCOPY", Inorganica Chimica Acta, 276(1-2), 1998, pp. 215-221

Abstract

Escherichia coli L-threonine dehydrogenase (TDH) is a homotetrameric protein which contains one Zn2+ ion per subunit and is a member of themedium chain, Zn2+-containing alcohol/polyol dehydrogenase family. TDH was subjected to extended X-ray absorption fine structure (EXAFS) spectroscopic analyses to explore what residues might bind the Zn2+; theEXAFS data are consistent with a tetrathiolate ligation sphere for the zinc atom. As a test of this proposed model, the oxidation state of the six cysteine residues in the enzyme was evaluated. Under typical storage conditions (4 degrees C with intermittent exposure to air; 50 mM Tris-HCl buffer, pH 8.4; 5 mM 2-mercaptoethanol, 2-ME) the TDH cysteine residues undergo air-dependent oxidation to form one disulfide bond/subunit with no change in enzymatic activity. Measurements of the free thiol and disulfide levels during storage support this proposal. Nodisulfide bond forms in TDH when it is stored for up to 100 days at 4degrees C under argon either with or without 5 mM 2-ME. The previously reported selective reactivity of Cys38 in native TDH towards either iodoacetate or Woodward's reagent K suggests that this residue is not involved in disulfide bond formation. The EXAFS data reported here andthe thiol/disulfide levels determined for TDH, together with the homology of TDH to horse Liver alcohol dehydrogenase, suggest that the oneZn2+/subunit of TDH is non-catalytic and is probably bound by cysteine residues 93, 96, 99, and 107 in a structural zinc-binding loop of the protein. (C) 1993 Elsevier Science S.A. All rights reserved.

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Documento generato il 04/12/20 alle ore 09:19:24