Exam 22: Protein Synthesis, Posttranslational Modification, and Transport

An analysis of noncanonical base pairings between the 5 ^' -position of the tRNA anticodon and the 3 ^' -position of the mRNA codon would show the pairing

Gene expression can be controlled by the modification of histones by all of the following EXCEPT

An inhibitor of would specifically prohibit the release of Ran from importin.

All aminoacyl-tRNA synthetases are

At any time during nuclear import and export, Ran can be found associated with all EXCEPT

Differentiate between type I and type II aminoacyl-tRNA synthetases in how they interact with the tRNA and acceptor stem.

A nucleophilic amino group of the amino acid bound to the 3 ^' terminus of A-site tRNA attacks the electrophilic carbonyl carbon in the ester bond between the 3 ^' terminus of P-site tRNA and its bound amino acid during the step of translation.

Enzyme-mediated protein modification in eukaryotic cells is a means of regulating the activity of the protein. Which of the following is UNLIKELY to result from such a modification?

A is NOT a characteristic of the ER signal peptide sequence.

The eukaryotic 48S preinitiation complex is purified and the components are identified. Which of the following would be found in this complex?

What step in the process of translation of a nascent protein into the lumen of the ER requires an input of energy provided by the hydrolysis of GTP?

Which base location in the figure below is LEAST discriminating in the bases that it can pair with as described by the wobble hypothesis?

During the import of one protein from the cytosol to the nucleus via Ran-dependent nuclear import, __________ high-energy phosphate molecule(s) are hydrolyzed.

The Shine-Dalgarno sequence of mRNA base pairs with the rRNA within the prokaryote __________ ribosomal subunit.

The $\Delta$ G $\degree$ ^' of the two combined catalytic steps of tRNA synthetase is near equilibrium. How does this reaction occur in an essentially irreversible fashion in a cell?

Radioactively labeled aminoacyl-tRNAs were used in the Nirenberg-Leder experiment to assign triplet codons to specific amino acids. If the aminoacyl-tRNA contains an anticodon of AGG and the mRNA included contains a codon of UCA, where will the radioactivity be located at the end of the experiment? Explain your reasoning.

What is the identity of the protein labeled with the question mark in the eukaryotic preinitiation complex shown below?

What region of the amino acid below would become covalently attached to a tRNA?

Draw out the peptidyl transferase reaction that is catalyzed by the ribozyme activity of the 23S rRNA in the large ribosomal subunit.

Why does the genetic code require triplet codons to code for the 20 different amino acids? Why would duplet codons be inadequate to perform the job?