LOW UNSATURATION LEVEL OF THYLAKOID MEMBRANE-LIPIDS LIMITS TURNOVER OF THE D1 PROTEIN OF PHOTOSYSTEM-II AT HIGH IRRADIANCE

Turnover of the D1 protein of photosystem II (PSII) was studied in mutants of Synechocystis sp, PCC 6803 defective in the desaturation of thylakoid membrane lipids. The lack of polyunsaturated fatty acids from membranes made PSII extremely susceptible to photoinhibition and caused a significant reduction in the D1 protein content of the thylakoid membranes at high irrradiances. These results may be attributed to an impaired function in the protein synthesis machinery, most probably at the translational or posttranslational level.