Organization of the photosystem II centers and their associated antennae in the thylakoid membranes: a comparative ultrastructural, biochemical, and biophysical study of Chlamydomonas wild type and mutants lacking in photosystem II reaction centers.

Abstract

The ultrastructure of thylakoid membranes that lacked either some or all of their photosystem [PS] II centers in the F34SU3 and F34 mutants of C. reinhardtii was investigated. There are no particles of the 160-.ANG. size class on the EF [exoplasmic face] of the thylakoids in the absence of PSII centers (as in F34), the F34SU3 contains 50% of the wild-type number of PSII centers and EF particles. The density of the particles on the PF [protoplasmic face] of the thylakoids is higher in the mutants than in the wild type. The fluorescence analysis shows that the organization of the pigments is the same regardless of whether 50% of the PSII centers are temporarily inactivated (by preilluminating the wild type) or are actually missing from the thylakoid membrane (F34SU3). Apparently, each 160-.ANG. EF particle has only one PSII center surrounded by light-harvesting complexes and part of the PSII antenna is associated with 80-.ANG. PF particles in both of the mutants and the wild type.