Identification of a new protein synthesis initiation factor from wheat germ.

A previously unidentified factor has been isolated from wheat germ that stimulates globin mRNA-directed polypeptide synthesis in vitro. This factor is separated from eukaryotic initiation factor (eIF)-4B by chromatography on m7GTP-Sepharose. eIF-4B binds to m7GTP-Sepharose, whereas the stimulatory factor does not. Further purification of the factor yields a preparation that contains one major polypeptide with a molecular weight of approximately 59,000, This factor enhances the binding of globin mRNA to 40 S ribosomal subunits in the presence of eIF-2, eIF-3, eIF-4A, and either eIF-4B or eIF-4F and has been designated eIF-4G.