Purification properties and biogenesis of Chlamydomonas reinhardii photosystem I reaction center.

A photosystem I reaction center was isolated from Chlamydomonas reinhardii chloroplasts. It consists of four different polypeptides with Mr approximately 70,000 (subunit I), 19,000 (subunit II), 10,000 (subunit III), and 8,000 (subunit IV). In the presence of salts, the purified reaction center was active in cytochrome 552 photooxidation. Short term labeling experiments with [35S]sulfate revealed that subunit III contains no cysteine or methionine. Subunits I and IV were shown to be chloroplast translation products, while subunit II appears to be synthesized on cytoplasmic ribosomes. The site of synthesis of the subunits to the proton-ATPase complex was studied. A differential effect of cycloheximide on the assembly of photosystem I reaction center and the proton-ATPase complex was indicated.