mRNA binding properties of wheat germ protein synthesis initiation factor 2

The binding of protein synthesis initiation factor (eIF-) 2 to mRNA was measured by retention of the mRNA.eIF-2 complexes on nitrocellulose filters. The binding of eIF-2 to mRNA was inhibited by GDP and GTP; the inhibition by GTP was enhanced by the presence of Met-tRNA(i). In addition, the formation of eIF-2.GDP binary complex and eIF-2.GTP.Met-tRNA(i) ternary complex was inhibited by mRNA. These data indicate that mRNA binds to a site on eIF-2 that is the same or overlaps the site to which guanine nucleotides bind eIF-2. This finding strongly suggests that inhibition of ternary complex formation by mRNA may be the result of competition between mRNA and GTP and not competition between mRNA and Met-tRNA(i).