Gonsky R, Itamar D, Harary R, Kaempfer R. Binding of ATP and messenger RNA by the beta-subunit of eukaryotic initiation factor 2.
Biochimie 1992;
74:427-34. [PMID:
1637867 DOI:
10.1016/0300-9084(92)90082-p]
[Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In addition to forming a ternary complex with Met-tRNA(f) and GTP, eukaryotic initiation factor 2 (eIF-2) recognizes a specific site in mRNA molecules. Both binding activities are regulated by ATP, which itself binds tightly and specifically to eIF-2. Denaturation of eIF-2 with urea leads to complete loss of Met-tRNA(f) binding activity, while mRNA binding activity is stable. Hence, distinct conformational features in eIF-2 are required for ternary complex formation and for binding of mRNA. Chromatography of eIF-2 over ATP-agarose, in denaturing conditions that induce polypeptide subunit dissociation, results in selective retention of the beta-subunit of eIF-2. Isolated beta-subunit is capable of binding mRNA as well as ATP. Cibacron blue 3G-A binds tightly to eIF-2 and inhibits the binding of mRNA. This inhibition is relieved upon addition of ATP, showing that Cibacron blue 3G-A competes with ATP for eIF-2. eIF-2 beta subunit, active in binding of mRNA, is recovered upon chromatography of eIF-2 in denaturing conditions over matrix-bound Cibacron blue 3G-A. These results show that the ability of eIF-2 to bind mRNA and its ability to bind ATP are both lodged within remarkably stable domains of its beta-subunit. During initiation of protein synthesis, the eIF-2 beta subunit may thus interact with three ligands important for translational control: Met-tRNA(f), mRNA and ATP.
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