Elongation factor G initiates translocation through a power stroke.

Abstract

During the translocation step of prokaryotic protein synthesis, elongation factor G (EF-G), a guanosine triphosphatase (GTPase), binds to the ribosomal PRE-translocation (PRE) complex and facilitates movement of transfer RNAs (tRNAs) and messenger RNA (mRNA) by one codon. Energy liberated by EF-G's GTPase activity is necessary for EF-G to catalyze rapid and precise translocation. Whether this energy is used mainly to drive movements of the tRNAs and mRNA or to foster EF-G dissociation from the ribosome after translocation has been a long-lasting debate. Free EF-G, not bound to the ribosome, adopts quite different structures in its GTP and GDP forms. Structures of EF-G on the ribosome have been visualized at various intermediate steps along the translocation pathway, using antibiotics and nonhydolyzable GTP analogs to block translocation and to prolong the dwell time of EF-G on the ribosome. However, the structural dynamics of EF-G bound to the ribosome have not yet been described during normal, uninhibited translocation. Here, we report the rotational motions of EF-G domains during normal translocation detected by single-molecule polarized total internal reflection fluorescence (polTIRF) microscopy. Our study shows that EF-G has a small (∼10°) global rotational motion relative to the ribosome after GTP hydrolysis that exerts a force to unlock the ribosome. This is followed by a larger rotation within domain III of EF-G before its dissociation from the ribosome.

• Authors: Chunlai Chen, Xiaonan Cui, John F Beausang, Haibo Zhang, Ian Farrell, Barry S Cooperman, Yale E Goldman
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 113 Issue 27 Pg. 7515-20 (07 05 2016) ISSN: 1091-6490 [Electronic] United States
• PMID: 27313204 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Peptide Elongation Factor G
• Protein Translocation Systems
• Guanosine Triphosphate

Topics

• Amino Acid Sequence
• Guanosine Triphosphate (metabolism)
• Molecular Sequence Data
• Peptide Elongation Factor G (metabolism)
• Protein Translocation Systems
• Ribosomes (metabolism)