Visualization of elongation factor G on the Escherichia coli 70S ribosome: the mechanism of translocation.
During protein synthesis, elongation factor G (EF-G) binds to the ribosome and promotes the step of translocation, a process in which tRNA moves from the A to the P site of the ribosome and the mRNA is advanced by one codon. By using three-dimensional cryo-electron microscopy, we have visualized EF-G in a ribosome-EF-G-GDP-fusidic acid complex. Fitting the crystal structure of EF-G-GDP into the cryo density map reveals a large conformational change mainly associated with domain IV, the domain that mimics the shape of the anticodon arm of the tRNA in the structurally homologous ternary complex of Phe-tRNAPhe, EF-Tu, and a GTP analog. The tip portion of this domain is found in a position that overlaps the anticodon arm of the A-site tRNA, whose position in the ribosome is known from a study of the pretranslocational complex, implying that EF-G displaces the A-site tRNA to the P site by physical interaction with the anticodon arm.
Agrawal
R K
RK
Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY 12201-0509, USA.
Penczek
P
P
Grassucci
R A
RA
Frank
J
J
D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors / Q000737:chemistry / Q000235:genetics* / Q000648:ultrastructure; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012270:Ribosomes / Q000737:chemistry / Q000235:genetics* / Q000648:ultrastructure
D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors