Abstract
The green algal extrinsic 23 and 17 kDa proteins directly bound to photosystem II (PSII) independent of the other extrinsic proteins, which is largely different from those of spinach PSII (Suzuki et al., Plant Cell Physiol. 44, 76-84, 2003). In order to elucidate the possible causes responsible for the differences, cross-reconstitution experiments were performed with different combinations of the extrinsic proteins and the green algal (Chlamydomonas reinhardtii) or spinach PSII. These results showed that the green algal extrinsic proteins could not bind to spinach PSII directly, indicating that their direct binding depends principally on PSII intrinsic proteins. In addition, we performed crosslinking experiments with a water-soluble carbodiimide. These results showed that the extrinsic 23 kDa protein is in close proximity with the large subunit of cytchrome b559, indicating that the latter provided a possible binding site for the 23 kDa protein in the green algal PSII.
