Protein synthesis in chloroplasts. VII. Initiation of protein synthesis in isolated intact pea chloroplasts.

Isolated intact pea chloroplasts use light energy to synthesise N-formayl [35S]-methionylpuromycin when incubated with L-[35S]methionine and puromycin. Control experiments establish that this synthesis occurs on chloroplast ribosomes, and not on contaminating mitochondrial or bacterial ribosomes. The amount of N-formylmethionylpuromycin formed suggests that each messenger RNA that is being translated in vitro undergoes initiation at least twice. We conclude that isolated, intact pea chloroplasts carry out the initiation of protein synthesis, as well as the elongation and termination of polypeptide chains.