Association of chlorophyll a/ c2 complexes to photosystem I and photosystem II in the cryptophyte Rhodomonas CS24

Abstract

Photosynthetic supercomplexes from the cryptophyte Rhodomonas CS24 were isolated by a short detergent treatment of membranes from the cryptophyte Rhodomonas CS24 and studied by electron microscopy and low-temperature absorption and fluorescence spectroscopy. At least three different types of supercomplexes of photosystem I (PSI) monomers and peripheral Chl a/ c 2 proteins were found. The most common complexes have Chl a/ c 2 complexes at both sides of the PSI core monomer and have dimensions of about 17 × 24 nm. The peripheral antenna in these supercomplexes shows no obvious similarities in size and/or shape with that of the PSI–LHCI supercomplexes from the green plant Arabidopsis thaliana and the green alga Chlamydomonas reinhardtii, and may be comprised of about 6–8 monomers of Chl a/ c 2 light-harvesting complexes. In addition, two different types of supercomplexes of photosystem II (PSII) dimers and peripheral Chl a/ c 2 proteins were found. The detected complexes consist of a PSII core dimer and three or four monomeric Chl a/ c 2 proteins on one side of the PSII core at positions that in the largest complex are similar to those of Lhcb5, a monomer of the S-trimer of LHCII, Lhcb4 and Lhcb6 in green plants.