Exam 22: Protein Synthesis, Posttranslational Modification, and Transport

In an iteration of the Nirenberg-Leder experiment to assign triplet codons to specific amino acids, radioactively labeled aminoacyl-tRNA with the anticodon of CUG was used. The radioactivity was retained on the filter at the end of the experiment. Which mRNA was used in this iteration of the experiment?

What characteristics of eukaryotic mRNA are recognized through specific interactions during the formation of the translation initiation complex?

Where might the molecule shown below be located in both the prokaryotic and eukaryotic ribosome?

Nirenberg and Matthaei determined the genetic code experimentally by using a cell-free translation system. Two components, however, were restricted in their system. One was the use of a single type of mRNA. What was the other component that was restricted? How did this restriction allow them to determine the genetic code?

Which of the following catalyzes the formation of a bond between an amino acid and a tRNA?

Inosine is formed through a

Which protein would initially have been translated on free ribosomes?

The prokaryotic ribosome contains __________ subunits. The eukaryotic ribosome contains __________ subunits.

Place the following steps in the initiation phase in a prokaryote in their proper order. A. mRNA binds to the complex. B. GTP is hydrolyzed. C. IF1, IF2, and IF3 bind the 30S subunit.

Identify the antibiotic shown below and illustrate how it functions to inhibit bacterial cell growth.

Place the following steps in the elongation phase of translation in their proper order. A. Peptide bond formation occurs. B. GTP is hydrolyzed, and the ribosome moves one codon in the 3 ^' direction. C. GTP is hydrolyzed, and EF-Tu•GDP is released. D. tRNA is released from the E site.

Which of the following is NOT a component that is released from the ribosome on translation termination?

tRNA must be before binding to the ribosome to allow for translation to occur.

Below are seven examples of sequences found in E. coli. Differentiate between the underlined and bolded sequences. Explain where each would ultimately be located in the 70S initiation complex and what types of interactions are required to achieve these locations.

Place the following steps in proper order for the translation of a membrane-bound protein. A. GTP binds to SRP. B. Protein synthesis occurs on free ribosome. C. Protein synthesis halts. D. SRP binds to the signal peptide sequence.

Consider an in vitro experiment in which all components needed for protein synthesis are present. If tRNAs charged with radioactively labeled amino acids are added, over time the radioactivity would be located in which of the following components?

If the following mRNA was added to a cell-free translation system, how many unique protein sequences would be generated?

Eukaryotes are directed to begin scanning the mRNA for the start codon based on binding of the

Radioactively labeled aminoacyl-tRNAs were used in the Nirenberg-Leder experiment to assign triplet codons to specific amino acids. Why was this important in the experimental design?

Differentiate between the mechanisms of type I and type II aminoacyl-tRNA synthetases.