Abstract
Phycobilisome is a main light-harvesting complex in cyanobacteria and red algae. It has been suggested that phycobilisome transfers energy not only to PSII but also to PSI, although the molecular mechanism has not been elucidated. Previously, we reported that two rod-core linker proteins (CpcG1 and CpcG2) form distinct supramolecular complexes of phycobilisome in Synechocystis sp. PCC 6803. In contrast to the classic model, CpcG2-associated phycobilisome lacked core components and was suggested to serve as PSI antenna. We also showed that CpcG2 was predominantly associated with the isolated thylakoids, while CpcG1 was not tightly associated. Here, we solubilized and fractionated photosystems by glycerol density gradient centrifugation. The results suggest that CpcG2 is directly associated with PSI trimer. Specific interaction between CpcG2 and the thylakoid are also studied under various conditions. We will discuss the specific interaction of the CpcG2-phycobilisome and a possible mechanism of energy transfer to PSI.
