tailieunhanh - Báo cáo khoa học: Crystal structure of the halotolerant c-glutamyltranspeptidase from Bacillus subtilis in complex with glutamate reveals a unique architecture of the solvent-exposed catalytic pocket

c-Glutamyltranspeptidase (GGT; EC ), an enzyme found in organ-isms from bacteria to mammals and plants, plays a central role in glutathi-one metabolism. Structural studies of GGTs from Escherichia coliand Helicobacter pylori have revealed detailed molecular mechanisms of catalysis and maturation. | Crystal structure of the halotolerant c-glutamyltranspeptidase from Bacillus subtilis in complex with glutamate reveals a unique architecture of the solvent-exposed catalytic pocket Kei Wada1 Machiko Irie1 Hideyuki Suzuki2 and Keiichi Fukuyama1 1 Department of BiologicalSciences Graduate Schoolof Science Osaka University Japan 2 Division of Applied Biology Graduate Schoolof Science and Technology Kyoto Institute of Technology Japan Keywords electrostatic surface potential glutathione Ntn-hydrolase family salt-tolerant y-glutamyltranspeptidase Correspondence K. Fukuyama Department of Biological Sciences Graduate School of Science Osaka University Toyonaka Osaka 560-0043 Japan Fax 81 6 6850 5425 Tel 81 6 6850 5422 E-mail fukuyama@ Received 3 October 2009 revised 5 November 2009 accepted 8 December 2009 doi y-Glutamyltranspeptidase GGT EC an enzyme found in organisms from bacteria to mammals and plants plays a central role in glutathione metabolism. Structural studies of GGTs from Escherichia coli and Helicobacter pylori have revealed detailed molecular mechanisms of catalysis and maturation. In these two GGTs highly conserved residues form the catalytic pockets conferring the ability of the loop segment to shield the bound c-glutamyl moiety from the solvent. Here we have examined the Bacillus subtilis GGT which apparently lacks the amino acids corresponding to the lid-loop that are present in mammalian and plant GGTs as well as in most bacterial GGTs. Another remarkable feature of B. subtilis GGT is its salt tolerance it retains 86 of its activity even in 3 M NaCl. To better understand these characteristics of B. subtilis GGT we determined its crystal structure in complex with glutamate a product of the enzymatic reaction at A resolution. This structure revealed that unlike the E. coli and H. pylori GGTs the catalytic pocket of B. subtilis GGT has no segment that covers the bound glutamate .