1a3g

Publication Abstract from PubMed

The X-ray crystallographic structure of the branched-chain amino acid aminotransferase from Escherichia coli was determined by means of isomorphous replacement using the selenomethionyl enzyme as one of the heavy atom derivatives. The enzyme is a homo hexamer with D3 symmetry, and the polypeptide chain of the subunit is folded into two domains (small and large domains). The coenzyme, pyridoxal 5'-phosphate, resides at the domain interface, its re-face facing toward the protein. The active site structure shows that the following sites can recognize branched-chain amino acids and glutamate as substrates: (1) a hydrophobic core formed by Phe36, Tyr164, Tyr31*, and Val109* for a branched-chain; (2) Arg97 for an acidic side chain of glutamate; and (3) Tyr95 and two main chain NH groups of Thr257 and Ala258 for the alpha-carboxylate of substrates. Although the main chain conformation of the active site is homologous to that of D-amino acid aminotransferase, many of the active site residues are different between them.

Three-dimensional structure of Escherichia coli branched-chain amino acid aminotransferase at 2.5 A resolution.,Okada K, Hirotsu K, Sato M, Hayashi H, Kagamiyama H J Biochem. 1997 Apr;121(4):637-41. PMID:9163511^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.