Interrupted catalysis: the EF4 (LepA) effect on back-translocation.

ABSTRACT: EF4, although structurally similar to the translocase EF-G, promotes back-translocation of tRNAs on the ribosome and is important for bacterial growth under certain conditions. Here, using a coordinated set of in vitro kinetic measures, including changes in the puromycin reactivity of peptidyl-tRNA and in the fluorescence of labeled tRNAs and mRNA, we elucidate the kinetic mechanism of EF4-catalyzed back-translocation and determine the effects of the translocation inhibitors spectinomycin and viomycin on the process. EF4-dependent back-translocation proceeds from a post-translocation (POST) complex to a pre-translocation (PRE) complex via a four-step kinetic scheme (i.e., POST-->I(1)-->I(2)-->I(3)-->PRE, which is not the simple reverse of translocation). During back-translocation, movement

SUBMITTER: Liu H 

PROVIDER: S-EPMC3138200 | biostudies-literature | 2010 Mar

REPOSITORIES: biostudies-literature