Sequential synthesis of membrane polypeptides in chloroplast thylakoids of synchronized Chlorella pyrenoidosa cells

Synchronized Chlorella pyrenoidosa cells (strain 211-8b) were incubated for 15 min with [³H]leucine at different times after the start of the light period. Chloroplast membranes were isolated and the polypeptides of the thylakoid membranes separated by polyacrylamide gel electrophoresis. The distribution of the radioactive label incorporated in polypeptides at different times indicates a sequential synthesis of protein-chlorophyll complexes (CPC) of the chloroplast membrane proteins. Synthesis of CPC of photochemical systems I and II is promoted by light, whereas the synthesis of the polypeptide “K” falls down with the beginning of the light period. The experiments suggest for different polypeptides during the differentiation process an independent variation in the rates of synthesis or in the incorporation into the membrane.