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1. Introduction
2. Ribosomes and translation
3. Molecular composition of the ribosome
4. Why is the ribosome so big?
5. The ribosome has a big substrate
6. Crystal structure of the 70S ribosome
7. The mRNA channel in the 30S subunit
8. tRNA positions in the A, P & E sites
9. Location of the tRNA in the ribosome
10. Positions of A- and P-tRNA in the ribosome
11. Ribosome structural dynamics during translocation
12. Positions of tRNA in the ribosome
13. The hybrid states elongation cycle
14. States of tRNA binding during movement
15. Movement of tRNA through the ribosome
16. Distortion of tRNA structure by the ribosome
17. tRNA structure distortion by ribosomal P, E sites
18. The ribosome is a molecular machine
19. Translocational mechanics: the Ratchet model
20. The rachet model
21. tRNA predicted positions in cryo-EM experiment
22. Inferred relationship - ratcheting, hybrid states
23. Testing intersubunit movement using FRET
24. The FRET experiment
25. FRET experiment results
26. Changes between S6-L9 and S11-L9
27. Reversed donor and acceptor fluors
28. Peptidyl-tRNA deacylation by puromycin reaction
29. Peptidyl-tRNA deacylation causes rotation
30. Reaction of a hybrid-state complex with EF-G-GTP
31. Reversal of intersubunit rotation
32. Intersubunit movement in single ribosomes
33. Conclusions from FRET experiments
34. Testing the ratchet model for translocation
35. Positions of introduced cysteines in L2 and S6
36. Juxtaposition of cysteines across subunit interface
37. Testing the disulfide bridge formation
38. Disulfide crosslinking prevents subunit dissociation
39. Identification of the S6-L2 crosslink
40. Crosslinking prevents polypeptide synthesis
41. Crosslinked ribosomes (1)
42. Crosslinked ribosomes (2)
43. What about translocation?
44. Translocation assay
45. Intersubunit crosslinking prevents translocation (1)
46. Translocation assay (toeprinting)
47. Intersubunit crosslinking prevents translocation (2)
48. Relative movement is required for translocation
49. The strictly EF-G-dependent step of translocation
50. What defines the mechanism of translocation?
51. The peptidyl transferase inhibitor sparsomycin
52. Catalysis of translocation by sparsomycin
53. The energetics of translocation
54. tRNA interactions in the 50S E-site
55. E-tRNA interactions with the ribosome
56. Exit of the deacylated tRNA from the E-site
57. The elbow of E-site tRNA stacks on the L1 RNA
58. Large-scale movement of the L1 arm of 23S rRNA
59. Movement of 50S subunit in translocation
60. Acknowledgements
61. Center for Molecular Biology of RNA

Topics Covered

• Ribosomes and translation
• Molecular composition of the ribosome
• Why is the ribosome so big?
• The mRNA channel in the 30S subunit
• Positions of tRNA in the A-, P- and E-sites
• Structural dynamics of the ribosome during translocation
• The hybrid states elongation cycle
• tRNA binding during its movement through the ribosome
• The 70S ribosome
• Distortion of tRNA structure by the ribosome
• The ratchet model
• Cryo-EM experiment
• Inferred relationship between ratcheting and hybrid states
• FRET changes
• Intersubunit movement
• Testing the ratchet model for translocation
• Translocation assay
• What defines the mechanism of translocation
• Sparsomycin
• The energetics of translocation
• E-site tRNA
• The ribosome is a molecular machine

Links

Series:

• The Mechanisms of Ribosome Function

Categories:

• Biochemistry
• Cell Biology

Talk Citation

Noller, H. (2008, May 15). Translocation: movement of tRNA and mRNA through the ribosome [Video file]. In The Biomedical & Life Sciences Collection, Henry Stewart Talks. Retrieved June 11, 2025, from https://doi.org/10.69645/DRKE5756.
Export Citation (RIS)

Publication History

• Published on May 15, 2008
• Archived on May 28, 2025

Financial Disclosures

• Prof. Harry Noller has not informed HSTalks of any commercial/financial relationship that it is appropriate to disclose.