Conformational changes in the GTPase modules of the signal reception particle and its receptor drive initiation of protein translocation.

ABSTRACT: During cotranslational protein targeting, two guanosine triphosphatase (GTPase) in the signal recognition particle (SRP) and its receptor (SR) form a unique complex in which hydrolyses of both guanosine triphosphates (GTP) are activated in a shared active site. It was thought that GTP hydrolysis drives the recycling of SRP and SR, but is not crucial for protein targeting. Here, we examined the translocation efficiency of mutant GTPases that block the interaction between SRP and SR at specific stages. Surprisingly, mutants that allow SRP-SR complex assembly but block GTPase activation severely compromise protein translocation. These mutations map to the highly conserved insertion box domain loops that rearrange upon complex formation to form multiple catalytic interactions with the two GTPs

SUBMITTER: Shan SO 

PROVIDER: S-EPMC2064468 | biostudies-literature | 2007 Aug

REPOSITORIES: biostudies-literature