Spontaneous reverse movement of mRNA-bound tRNA through the ribosome.
During the translocation step of protein synthesis, a complex of two transfer RNAs bound to messenger RNA (tRNA-mRNA) moves through the ribosome. The reaction is promoted by an elongation factor, called EF-G in bacteria, which, powered by GTP hydrolysis, induces an open, unlocked conformation of the ribosome that allows for spontaneous tRNA-mRNA movement. Here we show that, in the absence of EF-G, there is spontaneous backward movement, or retrotranslocation, of two tRNAs bound to mRNA. Retrotranslocation is driven by the gain in affinity when a cognate E-site tRNA moves into the P site, which compensates the affinity loss accompanying the movement of peptidyl-tRNA from the P to the A site. These results lend support to the diffusion model of tRNA movement during translocation. In the cell, tRNA movement is biased in the forward direction by EF-G, which acts as a Brownian ratchet and prevents backward movement.
Konevega
Andrey L
AL
Institute of Physical Biochemistry, University of Witten/Herdecke, 58448 Witten, Germany.
Fischer
Niels
N
Semenkov
Yuri P
YP
Stark
Holger
H
Wintermeyer
Wolfgang
W
Rodnina
Marina V
MV
D020285:Cryoelectron Microscopy; D004926:Escherichia coli / Q000378:metabolism*; D008958:Models, Molecular; D009068:Movement; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000378:metabolism* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000378:metabolism* / Q000648:ultrastructure; D012343:RNA, Transfer / Q000378:metabolism* / Q000648:ultrastructure; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism* / Q000648:ultrastructure
D012329:RNA, Bacterial; D012333:RNA, Messenger; D012346:RNA, Transfer, Amino Acyl; C019037:tRNA, peptidyl-; D012343:RNA, Transfer