1dju
From Proteopedia
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CRYSTAL STRUCTURE OF AROMATIC AMINOTRANSFERASE FROM PYROCOCCUS HORIKOSHII OT3
Overview
Aromatic amino acid aminotransferase (ArATPh), which has a melting, temperature of 120 degrees C, is one of the most thermostable, aminotransferases yet to be discovered. The crystal structure of this, aminotransferase from the hyperthermophilic archaeon Pyrococcus horikoshii, was determined to a resolution of 2.1 A. ArATPh has a homodimer structure, in which each subunit is composed of two domains, in a manner similar to, other well characterized aminotransferases. By the least square fit after, superposing on a mesophilic ArAT, the ArATPh molecule exhibits a large, deviation of the main chain coordinates, three shortened alpha-helices, an, elongated loop connecting two domains, and a long loop transformed from an, alpha-helix, which are all factors that are likely to contribute to its, hyperthermostability. The pyridine ring of the cofactor pyridoxal, 5'-phosphate covalently binding to Lys(233) is stacked parallel to F121 on, one side and interacts with the geminal dimethyl-CH/pi groups of Val(201), on the other side. This tight stacking against the pyridine ring probably, contributes to the hyperthermostability of ArATPh. Compared with other, ArATs, ArATPh has a novel substrate specificity, the order of preference, being Tyr > Phe > Glu > Trp > His>> Met > Leu > Asp > Asn. Its relatively, weak activity against Asp is due to lack of an arginine residue, corresponding to Arg(292)* (where the asterisk indicates that this is a, residues supplied by the other subunit of the dimer) in pig cytosolic, aspartate aminotransferase. The enzyme recognizes the aromatic substrate, by hydrophobic interaction with aromatic rings (Phe(121) and Tyr(59)*) and, probably recognizes acidic substrates by a hydrophilic interaction, involving a hydrogen bond network with Thr(264)*.
About this Structure
1DJU is a Single protein structure of sequence from Pyrococcus horikoshii with PLP as ligand. Full crystallographic information is available from OCA.
Reference
The molecular structure of hyperthermostable aromatic aminotransferase with novel substrate specificity from Pyrococcus horikoshii., Matsui I, Matsui E, Sakai Y, Kikuchi H, Kawarabayasi Y, Ura H, Kawaguchi S, Kuramitsu S, Harata K, J Biol Chem. 2000 Feb 18;275(7):4871-9. PMID:10671523
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