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?
A) eIF-1
B) eIF-2B
C) eIF-4A
D) eIF-4E
E) eIF-4G

Question

Quizplus · Accepted Answer

eIF-2B is a guanine nucleotide exchange factor that facilitates the exchange of GDP for GTP on eIF-2, thus recycling it to its active form. The eIF-2 cycle consists of the translation initiation factors: eIF-2A and eIF-2B (also called guanine-nucleotide exchange factor, GEF). The cycle involves the binding of GTP by eIF-2A forming a complex that then interacts with the initiator methionyltRNA. When the initiator methionyl-tRNA is placed into the correct position of the 40S ribosomal subunit, the GTP is hydrolyzed (generating GDP and release of P_i) to provide the energy necessary to correctly position the incoming mRNA such that the initiator AUG codon and the initiator methionyl-tRNA anticodon are aligned. In order to regenerate an active eIF-2A for subsequent translation initiation events, the GDP must be exchanged for GTP. The exchange reaction is catalyzed by eIF-2B.

Control of the Rate of Translational Initiation Can Be Exerted