3deg

Publication Abstract from PubMed

EF4 (LepA) is an almost universally conserved translational GTPase in eubacteria. It seems to be essential under environmental stress conditions and has previously been shown to back-translocate the tRNAs on the ribosome, thereby reverting the canonical translocation reaction. In the current work, EF4 was directly visualized in the process of back-translocating tRNAs by single-particle cryo-EM. Using flexible fitting methods, we built a model of ribosome-bound EF4 based on the cryo-EM map and a recently published unbound EF4 X-ray structure. The cryo-EM map establishes EF4 as a noncanonical elongation factor that interacts not only with the elongating ribosome, but also with the back-translocated tRNA in the A-site region, which is present in a previously unseen, intermediate state and deviates markedly from the position of a canonical A-tRNA. Our results, therefore, provide insight into the underlying structural principles governing back-translocation.

A new tRNA intermediate revealed on the ribosome during EF4-mediated back-translocation.,Connell SR, Topf M, Qin Y, Wilson DN, Mielke T, Fucini P, Nierhaus KH, Spahn CM Nat Struct Mol Biol. 2008 Sep;15(9):910-5. PMID:19172743^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.