1e5q

From Proteopedia

Revision as of 14:00, 5 November 2007

TERNARY COMPLEX OF SACCHAROPINE REDUCTASE FROM MAGNAPORTHE GRISEA, NADPH AND SACCHAROPINE

Overview

BACKGROUND: The biosynthesis of the essential amino acid lysine in higher, fungi and cyanobacteria occurs via the alpha-aminoadipate pathway, which, is completely different from the lysine biosynthetic pathway found in, plants and bacteria. The penultimate reaction in the alpha-aminoadipate, pathway is catalysed by NADPH-dependent saccharopine reductase. We set out, to determine the structure of this enzyme as a first step in exploring the, structural biology of fungal lysine biosynthesis. RESULTS: We have, determined the three-dimensional structure of saccharopine reductase from, the plant pathogen Magnaporthe grisea in its apo form to 2.0 A resolution, and as a ternary complex with NADPH and saccharopine to 2.1 A resolution., Saccharopine reductase is a homodimer, and each subunit consists of three, domains, which are not consecutive in amino acid sequence. Domain I, contains a variant of the Rossmann fold that binds NADPH. Domain II folds, into a mixed seven-stranded beta sheet flanked by alpha helices and is, involved in substrate binding and dimer formation. Domain III is, all-helical. The structure analysis of the ternary complex reveals a large, movement of domain III upon ligand binding. The active site is positioned, in a cleft between the NADPH-binding domain and the second alpha/beta, domain. Saccharopine is tightly bound to the enzyme via a number of, hydrogen bonds to invariant amino acid residues. CONCLUSIONS: On the basis, of the structure of the ternary complex of saccharopine reductase, an, enzymatic mechanism is proposed that includes the formation of a Schiff, base as a key intermediate. Despite the lack of overall sequence homology, the fold of saccharopine reductase is similar to that observed in some, enzymes of the diaminopimelate pathway of lysine biosynthesis in bacteria., These structural similarities suggest an evolutionary relationship between, two different major families of amino acid biosynthetic pathway, the, glutamate and aspartate families.

About this Structure

1E5Q is a Single protein structure of sequence from Magnaporthe grisea with NDP and SHR as ligands. Active as Saccharopine dehydrogenase (NADP(+), L-glutamate-forming), with EC number 1.5.1.10 Structure known Active Sites: NPA, NPB, NPC, NPD, NPE, NPF, NPG, NPH, SCA, SCB, SCC, SCD, SCE, SCF, SCG and SCH. Full crystallographic information is available from OCA.

Reference

Crystal structure of saccharopine reductase from Magnaporthe grisea, an enzyme of the alpha-aminoadipate pathway of lysine biosynthesis., Johansson E, Steffens JJ, Lindqvist Y, Schneider G, Structure. 2000 Oct 15;8(10):1037-47. PMID:11080625

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