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[[Image:1szu.gif|left|200px]]
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[[Image:1szu.png|left|200px]]


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{{STRUCTURE_1szu|  PDB=1szu  |  SCENE=  }}  
{{STRUCTURE_1szu|  PDB=1szu  |  SCENE=  }}  


'''The structure of gamma-aminobutyrate aminotransferase mutant: V241A'''
===The structure of gamma-aminobutyrate aminotransferase mutant: V241A===




==Overview==
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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.
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{{ABSTRACT_PUBMED_15723541}}


==About this Structure==
==About this Structure==
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[[Category: Zhou, X.]]
[[Category: Zhou, X.]]
[[Category: Gaba-at]]
[[Category: Gaba-at]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May  3 09:19:42 2008''
 
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 17:50:42 2008''

Revision as of 14:50, 28 July 2008

File:1szu.png

Template:STRUCTURE 1szu

The structure of gamma-aminobutyrate aminotransferase mutant: V241A

Template:ABSTRACT PUBMED 15723541

About this Structure

1SZU is a Single protein structure of sequence from Escherichia coli. 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

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