Recherche de plusieurs transporteurs d'electrons, notamment des cytochromes b-559 et c-553, chez trois mutants non photosynthetiques de Chlamydomonas reinhardi

Abstract

Studies of several electron carriers, particularly cytochromes b-559 and c-553 in three non-photosynthetic mutants of Chlamydomonas reinhardi Biochemical and spectroscopic analyses were performed in order to investigate the electron-carrier contents of three non-photosynthetic mutants ( Fl 5, Fl 9 and Fl 15) of Chlamydomonas reinhardi. These mutants exhibit several physiological amomalies, which indicate a blocking of the internal electron transport close to Photoreaction II. Quinones and soluble proteins were analysed by chromatography. With the insoluble cell debris, difference absorption spectra were measured at 20° and at −190°. The plastoquinone A, soluble cytochrome c-553, plastocyanin, ferredoxin and ferredoxin-NADP + reductase contents of each mutant and of the wild type were comparable. Cytochrome b-559, also, was present in the four strains. But it appeared that the mutants Fl 9 and Fl 15 showed only traces of the insoluble (bound) form of cytochrome c-553; this insoluble form was present, in appreciable amounts, in the wild type and in the mutant Fl 5. The wild type contained about: I molecule of cytochrome b-559 per 130 molecules of chlorophyll ( a+ b) and I molecule of bound cytochrome c-553 per 500 molecules of chlorophyll. It seems probable that the mutants are affected by structural defects, wich may be of a different nature for Fl 9 and Fl 15, on the one hand, and for Fl 5 on the other. However, the possibility of the lack of an unknown electron carrier in these mutants cannot be ruled out.