Visualization of release factor 3 on the ribosome during termination of protein synthesis

Bruno Klaholz (1, 2) , Alexander Myasnikov (3) , Marin van Heel (2)

1 IGBMC - Institut de génétique et biologie moléculaire et cellulaire
2 Imperial College London
3 Belozersky Institute of Physico-Chemical Biology

Termination of protein synthesis by the ribosome requires two release factor (RF) classes. The class II RF3 is a GTPase that removes class I RFs (RF1 or RF2) from the ribosome after release of the nascent polypeptide. RF3 in the GDP state binds to the ribosomal class I RF complex, followed by an exchange of GDP for GTP and release of the class I RF. As GTP hydrolysis triggers release of RF3 (ref. 4), we trapped RF3 on Escherichia coli ribosomes using a nonhydrolysable GTP analogue. Here we show by cryo-electron microscopy that the complex can adopt two different conformational states. In 'state 1', RF3 is pre-bound to the ribosome, whereas in 'state 2' RF3 contacts the ribosome GTPase centre. The transfer RNA molecule translocates from the peptidyl site in state 1 to the exit site in state 2. This translocation is associated with a large conformational rearrangement of the ribosome. Because state 1 seems able to accommodate simultaneously both RF3 and RF2, whose position is known from previous studies, we can infer the release mechanism of class I RFs.

Domaines: Biochimie, Biologie Moléculaire

Bruno Klaholz, Alexander Myasnikov, Marin van Heel. Visualization of release factor 3 on the ribosome during termination of protein synthesis. Nature, 2004, 427 (6977), pp.862-865. ⟨10.1038/nature02332⟩. ⟨hal-04143704⟩