Turnover of the photosystem II D1 protein in higher plants under photoinhibitory and nonphotoinhibitory irradiance.

The turnover in vivo of the Photosystem II (PS II) reaction center D1 protein was investigated by [35S] methionine labeling of leaf discs of Brassica napus and subsequent analysis after thylakoid SDS-gel electrophoresis. The rate of D1 protein degradation was found to have a t1/2 of approximately 2 h, at an irradiance corresponding to the growth irradiance. The rate of D1 protein degradation was not increased further by prior photoinhibitory...