Requirements for in vitro reconstruction of protein synthesis.

Translation of f2am3 RNA and MS2 RNA in a system containing purified ribosomes and precharged aminoacyl-tRNA, does not occur in the presence of the "known" initiation (IF-1, IF-2 and IF-3), elongation (EF-Tu, EF-Ts and EF-G) and termination (RF-1, RF-2) factors. Translation in this system requires at least three additional protein factors. These are EF-P and the rescue protein as well as a previously undescribed factor we call W, which is found in the high-salt ribosomal eluate.