Isolation and sequence of the cDNAs encoding the subunits of the isozyme form of wheat protein synthesis initiation factor 4F.

The nucleotide sequences of the cDNAs for the two subunits, p82 and p28, of the isozyme form of wheat germ eukaryotic initiation factor 4F (eIF-(iso)4F) were determined. The cDNA for the p82 subunit encodes a polypeptide of 86,514 Da. The deduced amino acid sequence of p82 contains possible motifs for ATP binding, metal binding, and phosphorylation. The cDNA sequence for the small subunit, p28, which is a m7G cap-binding protein, encodes a polypeptide of 23,524 Da. The deduced amino acid sequence of p28 is similar (approximately 38%) to cap-binding proteins from yeast and mammals. The p28 of wheat eIF-(iso)4F does not contain a serine or threonine in the vicinity of the serine (Ser53) of mammalian cap-binding protein which is phosphorylated and shown to affect activity in mammalian cells.