Purification and characterization of protein synthesis initiation factor eIF-3 from wheat germ.

eIF-3 from wheat germ is a large multicomponent factor. It sediments at 15 S and is comprised of ten different polypeptides with an Mr value ranging from 26 000 to 135 000; five out of the ten seem to be present in a 1 : 1 stoichiometric ratio, whereas the others appear to occur approximately in a 0.5 to 1 ratio. The factor is active in a partially purified cell-free system derived from wheat germ and in a mammalian model assay system for the synthesis of methionyl puromycin.