Amino Acid incorporation by wheat chloroplasts.

Isolated chloroplasts from wheat leaves incorporate radioactive amino acids into protein. Both physiological and biochemical evidence show that contaminating bacteria are not responsible for the activity. Activity is best in plastids from 5-day-old or younger seedlings; a sharp drop usually occurs by day 6 or 7. The system requires added adenosine triphosphate, guanosine triphosphate and Mg(++), and is inhibited by ribonuclease, puromycin and chloramphenicol. Preliminary evidence is presented that polyribosomes are present in the young leaf chloroplast fraction. Half of the protein that is formed in a 20-minute incubation is released in soluble form.