1txx

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(New page: 200px<br /><applet load="1txx" size="450" color="white" frame="true" align="right" spinBox="true" caption="1txx, resolution 2.2&Aring;" /> '''ACTIVE-SITE VARIANT O...)
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Revision as of 01:33, 21 November 2007

Image:1txx.jpg

1txx, resolution 2.2Å

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ACTIVE-SITE VARIANT OF E.COLI THIOREDOXIN

Overview

The 2.2 A crystalline structure of an oxidized active-site variant of, Escherichia coli thioredoxin (Trx) has been solved. Trx is a 12 kDa enzyme, which catalyzes the oxidation of dithiols and the reduction and, isomerization of disulfides in other proteins. Its active site contains, the common structural motif CXXC. Protein-disulfide isomerase (PDI), a 57, kDa homolog of Trx, contains four Trx-like domains. The three-dimensional, structure of PDI is unknown. PDI-deficient Saccharomyces cerevisiae are, inviable. An active-site variant of Trx which complements PDI-deficient, yeast has the active-site sequence Cys32-Val33-Trp34-Cys35 (CVWC). The, reduction potential of oxidized CVWC Trx (E degrees ' = -0.230 V) is, altered significantly from that of the wild-type enzyme (E degrees ' =, -0.270 V). However, the structure of the oxidized CVWC enzyme is almost, identical to that of wild-type Trx. The addition of valine and tryptophan, in the active site is likely to increase the reduction potential, largely, by decreasing the pK(a) of the Cys32 thiol in the reduced enzyme. Unlike, in wild-type Trx, significant protein-protein contacts occur in the, crystal. Protein molecules related by a crystallographic twofold axis form, a dimer in the crystal. The dimer forms as an extension of the twisted, mixed beta-sheet which composes the backbone of each Trx structure.

About this Structure

1TXX is a Single protein structure of sequence from Escherichia coli with CU as ligand. Full crystallographic information is available from OCA.

Reference

The CXXC motif: crystal structure of an active-site variant of Escherichia coli thioredoxin., Schultz LW, Chivers PT, Raines RT, Acta Crystallogr D Biol Crystallogr. 1999 Sep;55(Pt 9):1533-8. PMID:10489448

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