Effect of ligands on the conformative response in E. coli GMP synthetase

CHED 226

AuBrei J. Weigand, ajw001@lvc.edu, Chemistry Department, Lebanon Valley College, 101 North College Avenue, Annville, PA 17003 and Owen A. Moe, moe@lvc.edu, Department of Chemistry, Lebanon Valley College, 101 North College Avenue, Annville, PA 17003.
GMP synthetase (GMPS), which catalyzes a terminal step in the purine de novo pathway, consists of a glutamine amidotransferase (GAT) domain that hydrolyzes glutamine and an ATP pyrophosphatase (ATPP) domain that forms an adenyl-XMP intermediate that reacts with ammonia produced by the GAT domain. A “conformative response” is induced by the binding of nucleotides to the ATPP domain, activating glutamine hydrolysis on the GAT domain. We have employed an HPLC assay to study the conformative response by measuring the kinetics of glutamine hydrolysis as it is affected by ligand binding to ATPP. We have also studied the kinetics of a cloned GAT domain. Our results suggest that the binding of XMP and the pyrophosphate moiety of ATP are minimally essential for the conformative response. We conclude from Km measurements that the conformative response has little effect on glutamine binding, but instead increases the maximal velocity of glutamine hydrolysis.
 

Undergraduate Research Poster Session: Biochemistry
2:30 PM-4:30 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Poster

Division of Chemical Education

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006