2z1z

From Proteopedia

Revision as of 10:58, 23 January 2008

Crystal structure of LL-Diaminopimelate Aminotransferase from Arabidopsis thaliana complexed with L-malate ion

Overview

The essential biosynthetic pathway to l-Lysine in bacteria and plants is, an attractive target for the development of new antibiotics or herbicides, because it is absent in humans, who must acquire this amino acid in their, diet. Plants use a shortcut of a bacterial pathway to l-Lysine in which, the pyridoxal-5'-phosphate (PLP)-dependent enzyme ll-diaminopimelate, aminotransferase (LL-DAP-AT) transforms l-tetrahydrodipicolinic acid, (L-THDP) directly to LL-DAP. In addition, LL-DAP-AT was recently found in, Chlamydia sp., suggesting that inhibitors of this enzyme may also be, effective against such organisms. In order to understand the mechanism of, this enzyme and to assist in the design of inhibitors, the, three-dimensional crystal structure of LL-DAP-AT was determined at 1.95 A, resolution. The cDNA sequence of LL-DAP-AT from Arabidopsis thaliana, (AtDAP-AT) was optimized for expression in bacteria and cloned in, Escherichia coli without its leader sequence but with a C-terminal, hexahistidine affinity tag to aid protein purification. The structure of, AtDAP-AT was determined using the multiple-wavelength anomalous dispersion, (MAD) method with a seleno-methionine derivative. AtDAP-AT is active as a, homodimer with each subunit having PLP in the active site. It belongs to, the family of type I fold PLP-dependent enzymes. Comparison of the active, site residues of AtDAP-AT and aspartate aminotransferases revealed that, the PLP binding residues in AtDAP-AT are well conserved in both enzymes., However, Glu97* and Asn309* in the active site of AtDAP-AT are not found, at similar positions in aspartate aminotransferases, suggesting that, specific substrate recognition may require these residues from the other, monomer. A malate-bound structure of AtDAP-AT allowed LL-DAP and, L-glutamate to be modelled into the active site. These initial, three-dimensional structures of LL-DAP-AT provide insight into its, substrate specificity and catalytic mechanism.

About this Structure

2Z1Z is a Single protein structure of sequence from Arabidopsis thaliana with and as ligands. Active as LL-diaminopimelate aminotransferase, with EC number 2.6.1.83 Full crystallographic information is available from OCA.

Reference

Crystal Structure of ll-Diaminopimelate Aminotransferase from Arabidopsis thaliana: A Recently Discovered Enzyme in the Biosynthesis of l-Lysine by Plants and Chlamydia., Watanabe N, Cherney MM, van Belkum MJ, Marcus SL, Flegel MD, Clay MD, Deyholos MK, Vederas JC, James MN, J Mol Biol. 2007 May 26;. PMID:17583737

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