Protein Synthesis

  • Translation basics – process by which mRNA is translated into an amino acid sequence using a ribosome (rRNAs and proteins) and tRNAs.

  • Understand the general structure of an amino acid, the peptide bond, and the genetic code (that three nucleotides make a codon and specify an amino acid). How does the tRNA interact with the codon? How does a tRNA become charged with an amino acid? What are the A, P, and E sites in a ribosome, and what happens at each of these three sites?

  • Initiating translation in prokaryotes: the small subunit binds the Shine-Dalgarno sequence, the initiator met binds, then the large subunit binds. The first AUG after the Shine Dalgarno sequence is the start codon. What do factors EF-T and EF-G do? Release factors recognize the stop codons, and allow the ribosome to dissociate.

  • What is a polysome?

  • Why are bacteria able to couple transcription and translation (how can transcription and translation of the same mRNA occur at the same time)? Can this happen in eukaryotes?

  • Eukaryotic translation does not use a Shine Dalgarno sequence; instead initiation complex forms at the 5'cap, and the first AUG after the cap becomes the start site. Elongation factors also help bring in the next tRNA and move the tRNAs from the A and P sites to the P and E sites. Does translation end the same way for both prokaryotes and eukaryotes?

  • What is a tmRNA and how does it ‘unstick’ stalled ribosomes in prokaryotes?

  • How do prokaryotes and eukaryotes slow/stop protein synthesis?

  • Post-translational modifications to amino acids increase the type of functions and activities the proteins can have. Identify three types of post-translational modification.

  • Chaperonins assist in protein folding. Understand the difference between those that "hold" the protein and those that "fold" the protein.

  • Sequences within protein sequence can (1) get the protein into the correct location for its function and (2) tag the protein for degradation. Signal sequences are usually located at the N’-terminus of proteins – what do they cause to happen? Ubiquitin tags have a very different purpose – what will happen to a protein labeled with ubiquitin?