Functional Organization of the Chlorophyll-Containing Complexes of Chlamydomonas reinhardi

Abstract

The stepwise synthesis and assembly of photosynthetic membrane components in the y-I mutant of C. reinhardi were previously demonstrated (OhaD 1975). This experimental system was used to investigate the process of formation and interconnection of the energy collecting chlorophylls [Chl] with the reaction centers of photosystems [PS] I and II. Photosynthetic electron flow at various light intensities, including parts or the entire electron transfer chain; analysis of the kinetics of fluorescence emission at room temperature and fluorescence emission spectra at 77.degree. K and electrophoretic separation of membrane polypeptides and chlorophyll protein complexes were measured. Evidently, each photosystem (PSI and PSII) contains, in addition to the reaction center, an interconnecting antenna and a main or light harvesting antenna complex. The formation of the light harvesting complex, interconnecting antenna and reaction centers for each PS can occur independently. The interconnecting antennae link the light harvesting complexes with the respective reaction centers. In their absence, energy transfer between the light harvesting Chl and the reaction centers is inefficient. The formation of the interconnecting antennae and efficient assembly of PS components occur simultaneously with the de novo synthesis of chlorophyll and at least 3 polypeptides, 1 translated in the cytoplasm and 2 translated in the chloroplast. The synthesis of these polypeptides was light-dependent.