A protein of molecular weight 78,000 bound to the polyadenylate region of eukaryotic messenger RNAs.

Two distinct proteins were found to be tightly bound to the heterogeneous messenger RNAs associated with polysomes in mouse L cells and rat hepatocytes. The molecular weight (78,000) of the larger of these two proteins is identical to that of the protein previously found associated with rabbit globin messenger RNA. This protein is shown to be bound to the adenylate-rich region of messenger RNA. The molecular weight of the smaller protein associated with messenger RNAs from hepatic and L-cell polysomes is similar to that found in globin messenger ribonucleoprotein.