1szu

From Proteopedia

proteopedia linkproteopedia link

spinqualitylabelsall models 1szu, resolution 2.52Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

The structure of gamma-aminobutyrate aminotransferase mutant: V241A

Overview

The E. coli isozyme of gamma-aminobutyrate aminotransferase (GABA-AT) is a, tetrameric pyridoxal phosphate-dependent enzyme that catalyzes, transamination between primary amines and alpha-keto acids. The roles of, the active site residues V241, E211, and I50 in the GABA-AT mechanism have, been probed by site-directed mutagenesis. The beta-branched side chain of, V241 facilitates formation of external aldimine intermediates with primary, amine substrates, while E211 provides charge compensation of R398, selectively in the primary amine half-reaction and I50 forms a hydrophobic, lid at the top of the substrate binding site. The structures of the I50Q, V241A, and E211S mutants were solved by X-ray crystallography to, resolutions of 2.1, 2.5, and 2.52 A, respectively. The structure of, GABA-AT is similar in overall fold and active site structure to that of, dialkylglycine decarboxylase, which catalyzes both transamination and, decarboxylation half-reactions in its normal catalytic cycle. Therefore, an attempt was made to convert GABA-AT into a decarboxylation-dependent, aminotransferase similar to dialkylglycine decarboxylase by systematic, mutation of E. coli GABA-AT active site residues. Two of the twelve, mutants presented, E211S/I50G/C77K and E211S/I50H/V80D, have approximately, 10-fold higher decarboxylation activities than the wild-type enzyme, and, the E211S/I50H/V80D has formally changed the reaction specificity to that, of a decarboxylase.

About this Structure

1SZU is a Single protein structure of sequence from Escherichia coli with SO4, EDO, PLP and PMP as ligands. Active as 4-aminobutyrate transaminase, with EC number 2.6.1.19 Full crystallographic information is available from OCA.

Reference

Kinetic and crystallographic analysis of active site mutants of Escherichia coli gamma-aminobutyrate aminotransferase., Liu W, Peterson PE, Langston JA, Jin X, Zhou X, Fisher AJ, Toney MD, Biochemistry. 2005 Mar 1;44(8):2982-92. PMID:15723541

Page seeded by OCA on Wed Nov 21 02:52:55 2007