3zzk | pdb_00003zzk

Structure of an engineered aspartate aminotransferase

spinqualitylabelsall models 3zzk, resolution 1.78Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3zzk is a 1 chain structure with sequence from Escherichia coli. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: GOL, PMP, SO4 Related: 1arg, 1aam, 1toe, 1ix7, 1cq6, 1asn, 1g7x, 1ahx, 1asg, 1ahy, 1qis, 1g7w, 1qir, 1ahe, 1ase, 1ams, 2aat, 1arh, 1ari, 1ix8, 1bqd, 1asb, 1cq8, 1asd, 1asa, 1ahf, 1art, 1toi, 1aib, 5eaa, 1czc, 1ix6, 1asm, 1yoo, 1asf, 1g4x, 1c9c, 1b4x, 1bqa, 1spa, 1aic, 1tok, 1toj, 1cq7, 1ars, 1aaw, 1g4v, 1aia, 1asl, 1asc, 3aat, 1tog, 1amr, 1cze, 1qit, 1amq, 1ahg, 3zzj, 4a00 Activity: Aspartate transaminase, with EC number 2.6.1.1 Resources: FirstGlance, OCA, RCSB, PDBsum Publication Abstract from PubMed The joint substitution of three active-site residues in Escherichia colil-aspartate aminotransferase increases the ratio of l-cysteine sulfinate desulfinase to transaminase activity 10(5)-fold. This change in reaction specificity results from combining a tyrosine-shift double mutation (Y214Q/R280Y) with a non-conservative substitution of a substrate-binding residue (I33Q). Tyr214 hydrogen bonds with O3 of the cofactor and is close to Arg374 which binds the alpha-carboxylate group of the substrate; Arg280 interacts with the distal carboxylate group of the substrate; and Ile33 is part of the hydrophobic patch near the entrance to the active site, presumably participating in the domain closure essential for the transamination reaction. In the triple-mutant enzyme, k(cat)' for desulfination of l-cysteine sulfinate increased to 0.5s(-1) (from 0.05s(-1) in wild-type enzyme), whereas k(cat)' for transamination of the same substrate was reduced from 510s(-1) to 0.05s(-1). Similarly, k(cat)' for beta-decarboxylation of l-aspartate increased from<0.0001s(-1) to 0.07s(-1), whereas k(cat)' for transamination was reduced from 530s(-1) to 0.13s(-1). l-Aspartate aminotransferase had thus been converted into an l-cysteine sulfinate desulfinase that catalyzes transamination and l-aspartate beta-decarboxylation as side reactions. The X-ray structures of the engineered l-cysteine sulfinate desulfinase in its pyridoxal-5'-phosphate and pyridoxamine-5'-phosphate form or liganded with a covalent coenzyme-substrate adduct identified the subtle structural changes that suffice for generating desulfinase activity and concomitantly abolishing transaminase activity toward dicarboxylic amino acids. Apparently, the triple mutation impairs the domain closure thus favoring reprotonation of alternative acceptor sites in coenzyme-substrate intermediates by bulk water. Structure and mechanism of a cysteine sulfinate desulfinase engineered on the aspartate aminotransferase scaffold.,Fernandez FJ, de Vries D, Pena-Soler E, Coll M, Christen P, Gehring H, Vega MC Biochim Biophys Acta. 2011 Nov 23;1824(2):339-349. PMID:22138634 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Aspartate Aminotransferase

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