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Chapter 37: Translation: Protein Synthesis and Modification

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?

A. amino acid activation by attachment to a tRNA

B. correct alignment of the mRNA on the 40S ribosome

C. formation of the 80S initiation complex

D. formation of the peptide bond

E. translocation of the ribosome

Answer E: The process of moving the peptidyl-tRNA from the A-site to the P-site is termed translocation. Translocation is catalyzed by eEF-2 coupled to GTP hydrolysis. In the process of translocation the ribosome is moved along the mRNA such that the next codon of the mRNA resides under the A-site. Following translocation eEF-2 is released from the ribosome. The cycle can now begin again.

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?

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ACA threonine (T) CAU histidine (H)
ACG threonine (T) CUA leucine (L)
AUG methionine (M) CGU arginine (R)
AAU asparagine (N) CCU proline (P)
AGG arginine (R) UGC cysteine (C)
AUA isoleucine (I) UGU cysteine (C)
GGA glycine (G) UAU tyrosine (Y)
GUA valine (V) UAC tyrosine (Y)
GCA alanine (A) UCC serine (S)
UGG tryptophan (W)

A. C-T-I-P-Y

B. H-S-I-A-C

C. M-L-W-N

D. T-C-Y-G-M

E. V-R-Y-R-T

Answer C: Transcription of the DNA would result in the generation of an antiparallel complimentary strand of RNA where U would be inserted into the RNA at each location in the template DNA where there was an A. Translation in eukaryotic cells begins with methionine. Therefore, translation of the synthetic RNA in this study will begin at the first AUG codon encountered. The RNA resulting from the DNA would have the sequence 5′-ACAUGCUAUGGAAUG-3′. The only correct peptide is the one beginning with methionine.

Which of the following translation factors is responsible for engaging the cap structure of the mRNA?

A. eIF-2

B. eIF-2B

C. eIF-4E

D. eIF-4EBP (4EBP)

E. eIF-4G

Answer C:...

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