1aaw: Difference between revisions

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THE STRUCTURAL BASIS FOR THE ALTERED SUBSTRATE SPECIFICITY OF THE R292D ACTIVE SITE MUTANT OF ASPARTATE AMINOTRANSFERASE FROM E. COLI

OverviewOverview

Two refined crystal structures of aspartate aminotransferase from E. coli are reported. The wild type enzyme is in the pyridoxal phosphate (PLP) form and its structure has been determined to 2.4 A resolution, refined to an R-factor of 23.2%. The structure of the Arg292Asp mutant has been determined at 2.8 A resolution, refined to an R-factor of 20.3%. The wild type and mutant crystals are isomorphous and the two structures are very similar, with only minor changes in positions of important active site residues. As residue Arg292 is primarily responsible for the substrate charge specificity in the wild type enzyme, the mutant containing a charge reversal at this position might be expected to catalyze transamination of arginine as efficiently as the wild type enzyme effects transamination of aspartate [Cronin, C.N. and Kirsch, J.F. (1988) Biochemistry, 27, 4572-4579]. This mutant does in fact prefer arginine over aspartate as a substrate, however, the rate of catalysis is much slower than that of the wild type enzyme with its physiological substrate, aspartate. A comparison of these two structures indicates that the poorer catalytic efficiency of R292D, when presented with arginine, is not due to a gross conformational difference, but is rather a consequence of both small side chain and main chain reorientations and the pre-existing active site polar environment, which greatly favors the wild type ion pair interaction.

About this StructureAbout this Structure

1AAW is a Single protein structure of sequence from Escherichia coli with as ligand. Active as Aspartate transaminase, with EC number 2.6.1.1 Full crystallographic information is available from OCA.

ReferenceReference

The structural basis for the altered substrate specificity of the R292D active site mutant of aspartate aminotransferase from E. coli., Almo SC, Smith DL, Danishefsky AT, Ringe D, Protein Eng. 1994 Mar;7(3):405-12. PMID:7909946

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OCA

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-[[Image:1aaw.jpg|left|200px]]<br /><applet load="1aaw" size="450" color="white" frame="true" align="right" spinBox="true"
+[[Image:1aaw.jpg|left|200px]]<br /><applet load="1aaw" size="350" color="white" frame="true" align="right" spinBox="true"
 caption="1aaw, resolution 2.4&Aring;" />
 '''THE STRUCTURAL BASIS FOR THE ALTERED SUBSTRATE SPECIFICITY OF THE R292D ACTIVE SITE MUTANT OF ASPARTATE AMINOTRANSFERASE FROM E. COLI'''<br />
 ==Overview==
-Two refined crystal structures of aspartate aminotransferase from E. coli, are reported. The wild type enzyme is in the pyridoxal phosphate (PLP), form and its structure has been determined to 2.4 A resolution, refined to, an R-factor of 23.2%. The structure of the Arg292Asp mutant has been, determined at 2.8 A resolution, refined to an R-factor of 20.3%. The wild, type and mutant crystals are isomorphous and the two structures are very, similar, with only minor changes in positions of important active site, residues. As residue Arg292 is primarily responsible for the substrate, charge specificity in the wild type enzyme, the mutant containing a charge, reversal at this position might be expected to catalyze transamination of, arginine as efficiently as the wild type enzyme effects transamination of, aspartate [Cronin, C.N. and Kirsch, J.F. (1988) Biochemistry, 27, 4572-4579]. This mutant does in fact prefer arginine over aspartate as a, substrate, however, the rate of catalysis is much slower than that of the, wild type enzyme with its physiological substrate, aspartate. A comparison, of these two structures indicates that the poorer catalytic efficiency of, R292D, when presented with arginine, is not due to a gross conformational, difference, but is rather a consequence of both small side chain and main, chain reorientations and the pre-existing active site polar environment, which greatly favors the wild type ion pair interaction.
+Two refined crystal structures of aspartate aminotransferase from E. coli are reported. The wild type enzyme is in the pyridoxal phosphate (PLP) form and its structure has been determined to 2.4 A resolution, refined to an R-factor of 23.2%. The structure of the Arg292Asp mutant has been determined at 2.8 A resolution, refined to an R-factor of 20.3%. The wild type and mutant crystals are isomorphous and the two structures are very similar, with only minor changes in positions of important active site residues. As residue Arg292 is primarily responsible for the substrate charge specificity in the wild type enzyme, the mutant containing a charge reversal at this position might be expected to catalyze transamination of arginine as efficiently as the wild type enzyme effects transamination of aspartate [Cronin, C.N. and Kirsch, J.F. (1988) Biochemistry, 27, 4572-4579]. This mutant does in fact prefer arginine over aspartate as a substrate, however, the rate of catalysis is much slower than that of the wild type enzyme with its physiological substrate, aspartate. A comparison of these two structures indicates that the poorer catalytic efficiency of R292D, when presented with arginine, is not due to a gross conformational difference, but is rather a consequence of both small side chain and main chain reorientations and the pre-existing active site polar environment, which greatly favors the wild type ion pair interaction.
 ==About this Structure==
-AAW 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 PLP as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Aspartate_transaminase Aspartate transaminase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.6.1.1 2.6.1.1] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1AAW OCA].
+AAW 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=PLP:'>PLP</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Aspartate_transaminase Aspartate transaminase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.6.1.1 2.6.1.1] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1AAW OCA].
 ==Reference==
@@ Line 14: / Line 14: @@
 [[Category: Escherichia coli]]
 [[Category: Single protein]]
-[[Category: Almo, S.C.]]
+[[Category: Almo, S C.]]
-[[Category: Danishefsky, A.T.]]
+[[Category: Danishefsky, A T.]]
 [[Category: Ringe, D.]]
-[[Category: Smith, D.L.]]
+[[Category: Smith, D L.]]
 [[Category: PLP]]
 [[Category: aminotransferase]]
-''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Tue Nov 20 10:43:30 2007''
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 11:42:41 2008''