Question
A decrease in the level of heme leads to a reduction in globin synthesis in thses cell. Which of the following best explains this phenomenon?
A. RNA polymerase activity is decreased in reticulocytes by low heme.
B. The initiation factor eIF-2 becomes phosphorylated,reducing its level of activity.
C. Heme normally activates peptidyl transferase in reticulocytes.
D. A tRNA degrading enzyme is active in the absence of heme.
Show Answer
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Correct Answer » B
Explanation
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Thses cells are reticulocytes
One mechanism by which initiation of translation in eukaryotes is effected is by phosphorylation of a small set (S) residue in the alpha subunit of eIF-2. The factor eIF-2 requires activation by interaction with GTP. The energy of GTP hydrolysis is used during translational initiation, thereby allowing eIF-2 to have GDP bound instead of GTP. In order to reactivate eIF-2, the GDP must be exchanged for DTP.
