Biochemical characterization of a novel photosystem I complex in the green alga Chlamydomonas reinahrdtii.

Abstract

In higher plants and green algae, photosystem I (PSI) forms a PSI-LHCI supercomplex in the thylakod membranes. Three distinct PSI complexes were separated on sucrose density gradient from the dodecylmaltoside (DM) solubilized thylakoid extracts of C. reinhardtii. The smallest complex of 500 kDa lacks PsaK and has been identified as an assembly intermediate while the complex of 700 kDa is the most abundant and is the mature PSI-LHCI supercomplex. In the present study, an additional large PSI complex of more than 1000 kDa was identified. Stable separation of these PSI complexes under stronger solubilization conditions suggests that three distinct PSI complexes exist in vivo. Possible role and subunit structure of these distinct complexes will be discussed.