Abstract
Among several proteases in chloroplasts, an FtsH protease (FtsH2) was suggested to be involved in the degradation of photodamaged D1 protein under light stress. Here, we carried out Western analysis with spinach PSII membranes and core complexes using antibodies against the FtsH (DS9 from tobacco and VAR2 from Arabidopsis). The antibodies cross-reacted with a component of about 70 kDa, suggesting the presence of FtsH2 in the vicinity of PSII. Effects of chemical cross-linkers such as EDC [1-ethyl-3-(3-dimethylaminopropyl) carbodiimide] were examined during the light stress to PSII. The FtsH2 and the D1 protein cross-linked to form a large cross-linked products by the illumination of the PSII membranes. These results suggest that the photodamaged D1 protein is recognized as a substrate by the FtsH protease, are that D1 degradation takes place in the stacked region of thylakoids.
