IMMUNOCHEMICAL STUDIES ON THE CLP-PROTEASE IN CHLOROPLASTS - EVIDENCEFOR THE FORMATION OF A CLPC P COMPLEX/

Chloroplasts contain a proteolytic system whose activity is ATP-depend ent. The presence of genes encoding homologues of the ATP-dependent E. coli ClpA/P protease on the plastome and nuclear genome suggests that a similar protease is located in chloroplasts. Antibodies raised again st a recombinant chloroplast-encoded proteolytic ClpP subunit detect t his polypeptide in chloroplasts prepared from barley leaves or the euk aryotic algae Chlamydomonos reinhardtii and Eugleno gracitis. Co-immun oprecipitation experiments using the anti-ClpP antibody and an antibod y against the nuclear encoded regulatory ClpC component (a ClpA homolo gue) provide direct evidence for the existence of a ClpC/P complex in the chloroplast stroma. These results suggest that at least a part of the ATP-dependent proteolytic reactions in the chloroplast is catalyze d by an enzyme complex similar to the E.coli ClpA/P protease.