structural basis of the decamer architecture of a higher plant glutamine synthetase and substrate recognition mechanism

点击翻译按钮获取中文摘要

We studied GS1a isoenzyme of maize glutamine synthetase in this research. Residues around Phe150 are responsible for interactions between two pentamers and we prepared many alanine-mutant enzymes for these residues. As a result we found the alanine mutants with high Km values for residues at the location spanning the two-pentamer interaction region and the substrate glutamic acid entry region into the catalytic site. The former region is distant from the catalytic site and we obtained two good crystals of G241A and W243A mutant enzymes at 2. 10 A and 2. 80 A resolutions, respectively there. These crystal structures revealed that there is a region on the enzyme involved in the substrate affinity distinct from the catalytic site.