Abstract
Cyanidioschyzon merolae is a kind of unicellular primitive red alga, which whole genome was sequenced in 2004. Isolated photosystem II complex (PS II) of C. merolae contained four extrinsic proteins, PsbO, PsbQ, PsbV, and PsbU, such as other primitive red alga, Cyanidium caldarium. Crystal structures of PS II complexes from thermophilic cyanobacteria at atomic resolution have been reported from several laboratories. However, PsbQ subunit is missing in cyanobacteria. In the PS II of C. caldarium, PsbQ can directly bind to PS II intrinsic proteins essentially independent of the presence of other proteins. The localization of PsbQ subunit has been unknown yet. In this study, nearest neighbor relationships between PsbQ and PS II constituent subunits from C. melorae were investigated by means of crosslinking reagents. We obtained several crosslinking products, which detected by antibody analysis. The localization of the PsbQ subunit is now in progress.
