FtsY,the Signal Recognition Particle (SRP) receptor in bacteria,as a protein translocase,is known to facilitate the cotranslational protein targeting by recruiting SRP-protein complex to secYEG.We show in this work that the N terminus was dispensable for FtsY GTPase activity,and the N domain played an essential role in the GTPase activity of the NG domain.In addition,the S.scoelicolor FtsY was able to restore function in an E.coli mutant.However,its NG domain was not able to play any roles.