MBB 222 Lecture Notes - Lecture 32: Atp Hydrolysis, Peptide Synthesis, Ribosome
20 Dec 2018
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Lecture 32 Part 1: Ribosomes
- The A-, P- and E-sites are the three binding sites for tRNAs. They span both subunits.
- Ribosome slides along the mRNA in the 5’ →3’ direction ideally 3nt at a time,
synthesizing protein in the N→C-terminal direction.
Exit of new polypeptide from ribosome
The newly-synthesized polypeptide exits through a hydrophobic tunnel in the 50S subunit at the
site of peptide bond formation.
Bottom view of 50S subunit showing the tunnel in which the polypeptide leaves the ribosome.
The translation cycle
Step 1: Initiation
Assembly of the ribosome, mRNA, and the first tRNA
Large differences between prokaryotic and eukaryotic
Step 2: Elongation
Peptide synthesized throughout this stage prokaryotic and eukaryotic are similar
Step 3: Termination Peptide released at this stage
Step 4: Ribosome recycling Ribosomal subunits separated and prepared for the next cycle
Many G-proteins assist in translation
GTP hydrolysis releases the exact same amount of energy as ATP hydrolysis
These proteins all assist in the processes of translation. They use the energy of GTP hydrolysis
to make sure peptide synthesis proceeds in the forward direction.
Nomenclature notes:
IF = Initiation Factor
Document Summary
The a-, p- and e-sites are the three binding sites for trnas. Ribosome slides along the mrna in the 5" 3" direction ideally 3nt at a time, synthesizing protein in the n c-terminal direction. The newly-synthesized polypeptide exits through a hydrophobic tunnel in the 50s subunit at the site of peptide bond formation. Bottom view of 50s subunit showing the tunnel in which the polypeptide leaves the ribosome. Assembly of the ribosome, mrna, and the first trna. Peptide synthesized throughout this stage prokaryotic and eukaryotic are similar. Step 3: termination peptide released at this stage. Step 4: ribosome recycling ribosomal subunits separated and prepared for the next cycle. Gtp hydrolysis releases the exact same amount of energy as atp hydrolysis. These proteins all assist in the processes of translation. They use the energy of gtp hydrolysis to make sure peptide synthesis proceeds in the forward direction. If = initiation factor eif = eukaryotic initiation factor ef = elongation factor.
