Abstract
Photosystem II (PSII) performs important reactions in chloroplasts and cyanobacteria: production of oxygen from light-driven oxidation of water and electron transfer from water to plastoquinone. The precomplex of PSII is transformed into an active complex, which consists of more than 20 kinds of proteins, chlorophylls, metals and plastoquinones. PSII complex is constructed by attachment of the intrinsic proteins CP43/CP47 to core protein D1/D2, incorporation of several small subunits, and assembly of the water-splitting system. Recently the cyanobacterial PSII structure by X-ray crystallography was reported, but the process of how the components are assembled remains unknown. Here we report our study on an extrinsic protein Psb27, which plays an important role in building the water-splitting system. PSII complexes isolated from the strain expressing Histidine-tagged Psb27 were analyzed by Blue-Native PAGE and 2D SDS-PAGE, and the obtained results indicated that Psb27 binds to monomer complexes, which have different subunit compositions.
