1h2h

From Proteopedia

Revision as of 07:45, 3 February 2008

CRYSTAL STRUCTURE OF TM1643

Overview

The open reading frame TM1643 of Thermotoga maritima belongs to a large, family of proteins, with homologues in bacteria, archaea, and eukaryotes., TM1643 is found in an operon with two other genes that encode enzymes, involved in the biosynthesis of NAD. In several bacteria, the gene in the, position occupied by TM1643 encodes an aspartate oxidase (NadB), which, synthesizes iminoaspartate as a substrate for NadA, the next enzyme in the, pathway. The amino acid sequence of TM1643 does not share any recognizable, homology with aspartate oxidase or with other proteins of known functions, or structures. To help define the biological functions of TM1643, we, determined its crystal structure at 2.6A resolution and performed a series, of screens for enzymatic function. The structure reveals the presence of, an N-terminal Rossmann fold domain with a bound NAD(+) cofactor and a, C-terminal alpha+beta domain. The structural information suggests that, TM1643 may be a dehydrogenase and the active site of the enzyme is located, at the interface between the two domains. The enzymatic characterization, of TM1643 revealed that it possesses NAD or NADP-dependent dehydrogenase, activity toward l-aspartate but no aspartate oxidase activity. The product, of the aspartate dehydrogenase activity is also iminoaspartate. Therefore, our studies demonstrate that two different enzymes, an oxidase and a, dehydrogenase, may have evolved to catalyze the first step of NAD, biosynthesis in prokaryotes. TM1643 establishes a new class of amino acid, dehydrogenases.

About this Structure

1H2H is a Single protein structure of sequence from Thermotoga maritima with as ligand. Known structural/functional Site: . Full crystallographic information is available from OCA.

Reference

Aspartate dehydrogenase, a novel enzyme identified from structural and functional studies of TM1643., Yang Z, Savchenko A, Yakunin A, Zhang R, Edwards A, Arrowsmith C, Tong L, J Biol Chem. 2003 Mar 7;278(10):8804-8. Epub 2002 Dec 21. PMID:12496312

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