title: Alternating arginine-modulated substrate specificity in an engineered tyrosine aminotransferase.
abstract: Mutation of six residues of Escherichia coli aspartate aminotransferase results in substantial acquisition of the transamination properties of tyrosine amino-transferase without loss of aspartate transaminase activity. X-ray crystallographic analysis of key inhibitor complexes of the hexamutant reveals the structural basis for this substrate selectivity. It appears that tyrosine aminotransferase achieves nearly equal affinities for a wide range of amino acids by an unusual conformational switch. An active-site arginine residue either shifts its position to electrostatically interact with charged substrates or moves aside to allow access of aromatic ligands.
authors.affiliation: Department of Structural Biology, University of Basel, Switzerland.
authors.forename: V N
authors.initials: VN
authors.lastname: Malashkevich
authors.forename: J J
authors.initials: JJ
authors.lastname: Onuffer
authors.forename: J F
authors.initials: JF
authors.lastname: Kirsch
authors.forename: J N
authors.initials: JN
authors.lastname: Jansonius
mesh_terms: D001120:Arginine; D001219:Aspartate Aminotransferases / Q000378:metabolism*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology; D008024:Ligands; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D014444:Tyrosine Transaminase / Q000378:metabolism*
chemical_list: D008024:Ligands; D001120:Arginine; D001219:Aspartate Aminotransferases; D014444:Tyrosine Transaminase