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Exam 37: Translation: Protein Synthesis and Modification

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Question 21

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You are utilizing a cell culture system derived from a breast cancer tumor to examine the process of protein synthesis. You discover that short peptides are present in the P-site of the ribosome whenever there is an aminoacyl-tRNA in the A-site, but it takes several hours for new aminoacyl-tRNAs to enter the ribosome. These results are most likely to be the result of a highly defective form of which of the following proteins?

A) eIF-2
B) eIF-2
C) eEF-1α
D) eEF-1βγ
E) eEF-2

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Question 22

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Reticulocytes control the rate of globin synthesis as a consequence of the level of heme in the cell. This prevents globin protein from being made when there are insufficient amounts of heme. Which of the following best explains the effects of heme on protein synthesis in these cells?

A) a heme-controlled phosphatase dephosphorylates cap-binding factor, which prevents recognition of globin mRNA by the ribosomes
B) a tRNA degrading enzyme is active in the absence of heme
C) heme normally activates peptidyltransferase in reticulocytes
D) RNA polymerase activity is decreased in reticulocytes by low heme
E) the initiation factor eIF-2 becomes phosphorylated, reducing its level of activity

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Question 23

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During the development of B cells there is switch from the synthesis of membrane-bound immunoglobulin to a secreted form of immunoglobulin. This change occurs because the mRNA population encodes a protein missing which of the following sequence motifs?

Which of the following translation factors is the target of an interferon-mediated translational control mechanism?

Control of the rate of translational initiation can be exerted at the level of the activity of the GTPbinding and hydrolyzing initiation factor, eIF-2. The efficiency with which eIF-2 recycles between the active GTP-bound form and the inactive GDPbound form is controlled by which of the following translation factors?

Which of the following determines the sequence of a polypeptide synthesized by the polyribosome complex?

Which of the following describes the direction of translation of mRNAs and synthesis of protein on ribosomes?

At which of the following sites on a eukaryotic mRNA is translation most likely to begin?

Many proteins contain a specialized stretch of amino acids that are recognized by a protein complex called the signal recognition particle. Which of the following best describes the function of this complex during the synthesis of secretory proteins?

During the process of protein synthesis the elongating peptide is transferred to the incoming aminoacyltRNA by a peptidyltransferase activity. Which of the following components of the translational machinery is most likely to possess this enzymatic activity?

You are studying the function of a protein isolated from a lung tumor cell line and comparing it to the same protein from normal tissue. You find that the protein derived from the cancer cells does not carry out its correct function as a result of improper folding of the protein. Which of the following, involved in the prevention of aggregation and improper folding of newly synthesized proteins, is most likely to be defective in the lung cancer cells?

You are examining the mutational changes that occurred in a breast cancer cell line. You discover that there is a mutation in the gene encoding selenoprotein translation factor B (SelB) . Which of the following is most likely defective in these cells as a result of this mutation?

During the process of protein synthesis the factor eEF-2 induces the hydrolysis of GTP. The energy of this hydrolysis is coupled to which of the following?

You are studying the effects of chemical treatment of components of the translational machinery. You discover that one chemical in particular results in the conversion of the cysteine attached to a tRNA to alanine. Which of the following would best describe the results of this chemical-induced insertion of alanine into the resultant polypeptide?

Reading of the genetic code is dependent on recognition of a codon on which of the following?

The unfolded protein response is a stress response in the ER. This stress pathway results in a halt to global protein synthesis and the activation of translation of factors required to respond to the stress inducer. Which of the following proteins of translation is the primary target of the ER stress response?

You are studying the processes of protein synthesis via the use of a cell-free system and synthetic RNAs. You have introduced the following RNA to this system: 5′-AUAUAAUGACUAAAUAU-3′ Table of codons Aaa lysine Aau asparagine ACu threonine Aua isoleucine AuG methionine Uau tyrosine Cau leucine Using the above indicated codons, which of the following is the most likely sequence of the peptide synthesized in this system?

You are studying the process of protein synthesis in cultures of hepatocytes. During an experiment, you Observe that translation of certain mRNAs continues until a termination codon reside in the A-site of the ribosome. The liberation of the polypeptide chain at this point involves the eukaryotic releasing factor and hydrolysis of which of the following?

Which of the following occurs to mRNA molecules during protein synthesis?

If the DNA shown was transcribed and then translated in a eukaryotic in vitro translation system, what would be the composition of the resultant peptide? 5′-CATTCCATAGCATGT-3′