Isolation of two protein factors from maize involved in poly U-dependent polyphenylalanine synthesis by maize ribosomes.

Two protein factors, isolated from S-100 of maize shoots, were found to be required not only for a "Mg(2+) shift" for poly U-dependent polymerization of phenylalanine, but also for polyphenylalanine synthesis. They seem to be crude preparations of EF-1 and EF-2. The poly U-directed amino acid incorporation by washed ribosomes was completely dependent upon these factors.