1SZS

The structure of gamma-aminobutyrate aminotransferase mutant: I50Q

Summary for 1SZS

• Entry DOI: 10.2210/pdb1szs/pdb
• Related: 1SF2 1SFF 1SZK 1SZU
• Descriptor: 4-aminobutyrate aminotransferase, SULFATE ION, 1,2-ETHANEDIOL, ... (6 entities in total)
• Functional Keywords: gaba-at, transferase
• Biological source: Escherichia coli
• Total number of polymer chains: 4
• Total formula weight: 187847.24

Authors

Liu, W.,Peterson, P.E.,Langston, J.A.,Jin, X.,Zhou, X.,Fisher, A.J.,Toney, M.D. (deposition date: 2004-04-06, release date: 2005-03-01, Last modification date: 2021-10-27)

Primary citation

Liu, W.,Peterson, P.E.,Langston, J.A.,Jin, X.,Zhou, X.,Fisher, A.J.,Toney, M.D.
Kinetic and Crystallographic Analysis of Active Site Mutants of Escherichia coligamma-Aminobutyrate Aminotransferase.
Biochemistry, 44:2982-2992, 2005

PubMed Abstract: 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.

PubMed: 15723541
DOI: 10.1021/bi048657a

Experimental method

X-RAY DIFFRACTION (2.1 Å)