1szu

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(New page: 200px<br /><applet load="1szu" size="450" color="white" frame="true" align="right" spinBox="true" caption="1szu, resolution 2.52&Aring;" /> '''The structure of gam...)
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[[Image:1szu.gif|left|200px]]<br /><applet load="1szu" size="450" color="white" frame="true" align="right" spinBox="true"
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[[Image:1szu.gif|left|200px]]<br /><applet load="1szu" size="350" color="white" frame="true" align="right" spinBox="true"
caption="1szu, resolution 2.52&Aring;" />
caption="1szu, resolution 2.52&Aring;" />
'''The structure of gamma-aminobutyrate aminotransferase mutant: V241A'''<br />
'''The structure of gamma-aminobutyrate aminotransferase mutant: V241A'''<br />
==Overview==
==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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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==
==About this Structure==
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1SZU is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with SO4, EDO, PLP and PMP as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/4-aminobutyrate_transaminase 4-aminobutyrate transaminase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.6.1.19 2.6.1.19] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1SZU OCA].
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1SZU is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=SO4:'>SO4</scene>, <scene name='pdbligand=EDO:'>EDO</scene>, <scene name='pdbligand=PLP:'>PLP</scene> and <scene name='pdbligand=PMP:'>PMP</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/4-aminobutyrate_transaminase 4-aminobutyrate transaminase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.6.1.19 2.6.1.19] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1SZU OCA].
==Reference==
==Reference==
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[[Category: Escherichia coli]]
[[Category: Escherichia coli]]
[[Category: Single protein]]
[[Category: Single protein]]
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[[Category: Fisher, A.J.]]
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[[Category: Fisher, A J.]]
[[Category: Jin, X.]]
[[Category: Jin, X.]]
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[[Category: Langston, J.A.]]
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[[Category: Langston, J A.]]
[[Category: Liu, W.]]
[[Category: Liu, W.]]
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[[Category: Peterson, P.E.]]
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[[Category: Peterson, P E.]]
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[[Category: Toney, M.D.]]
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[[Category: Toney, M D.]]
[[Category: Zhou, X.]]
[[Category: Zhou, X.]]
[[Category: EDO]]
[[Category: EDO]]
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[[Category: gaba-at]]
[[Category: gaba-at]]
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''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Wed Nov 21 02:52:55 2007''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 15:08:17 2008''

Revision as of 13:08, 21 February 2008

Image:1szu.gif

1szu, resolution 2.52Å

Drag the structure with the mouse to rotate

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 , , and 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

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