THE FUNCTIONING OF THE SRP RECEPTOR FTSY IN PROTEIN-TARGETING IN ESCHERICHIA-COLI CORRELATED WITH ITS ABILITY TO BIND AND HYDROLYZE GTP

In this study, we have established that FtsY, the E. coli homolog of t he mammalian signal recognition particle (SRP) receptor, is a GTP-bind ing protein which displays intrinsic GTPase activity. GTP was found to influence the protease sensitivity of FtsY indicative of a conformati onal change. FtsY mutated in the 4th GTP-binding consensus element dis played reduced GTP-binding and -hydrolysis which correlated with a red uced ability to interact with SRP. Overexpression of the mutant protei ns had a stronger inhibitory effect on protein translocation than over expression of wild-type FtsY. These observations suggest that in E. co li GTP is important for proper functioning of FtsY in protein-targetin g.