1tok | pdb_00001tok

Maleic acid-bound structure of SRHEPT mutant of E. coli aspartate aminotransferase

spinqualitylabelsall models 1tok, resolution 1.85Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1tok is a 2 chain structure with sequence from "bacillus_coli"_migula_1895 "bacillus coli" migula 1895. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: MAE NonStd Res: LLP Related: 1toe, 1tog, 1toi, 1toj Gene: ASPC, B0928 ("Bacillus coli" Migula 1895) Activity: Aspartate transaminase, with EC number 2.6.1.1 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed Several mutant Escherichia coli aspartate aminotransferases (eAATases) have been characterized in the attempt to evolve or rationally redesign the substrate specificity of eAATase into that of E. coli tyrosine aminotransferase (eTATase). These include HEX (designed), HEX + A293D (design followed by directed evolution), and SRHEPT (directed evolution). The A293D mutation realized from directed evolution of HEX is here imported into the SRHEPT platform by site-directed mutagenesis, resulting in an enzyme (SRHEPT + A293D) with nearly the same ratio of k(cat)/K(m)(Phe) to k(cat)/K(m)(Asp) as that of wild-type eTATase. The A293D substitution is an important specificity determinant; it selectively disfavors interactions with dicarboxylic substrates and inhibitors compared to aromatic ones. Context dependence analysis is generalized to provide quantitative comparisons of a common substitution in two or more different protein scaffolds. High-resolution crystal structures of ligand complexes of HEX + A293D, SRHEPT, and SRHEPT + A293D were determined. We find that in both SRHEPT + A293D and HEX + A293D, the additional mutation holds the Arg 292 side chain away from the active site to allow increased specificity for phenylalanine over aspartate. The resulting movement of Arg 292 allows greater flexibility of the small domain in HEX + A293D. While HEX is always in the closed conformation, HEX + A293D is observed in both the closed and a novel open conformation, allowing for more rapid product release. Narrowing substrate specificity in a directly evolved enzyme: the A293D mutant of aspartate aminotransferase.,Chow MA, McElroy KE, Corbett KD, Berger JM, Kirsch JF Biochemistry. 2004 Oct 12;43(40):12780-7. PMID:15461450 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Aspartate Aminotransferase

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