Abstract
Phycobilisome is a light-harvesting chromoprotein complex in cyanobacteria. At the last meeting we reported the analysis of phycobilisomes that were isolated from a mutant of Synechococcus sp. PCC 7942 constitutively expressing HspA, a small heat-shock protein. We also examined interactions between HspA and phycobilisome in a purified system. Those results suggest that some components of phycobilisome interact with HspA.
In the present study, we attempted to identify targets of HspA in phycobilisome specifically. A mixture of purified phycobilisome and HspA was incubated for 15 min at 50oC in the presence of 0.3% H2O2. The mixture was fractionated by sucrose gradient ultracentrifugation and each fraction was analyzed by SDS-PAGE. The denaturation of phycobilisome resulted in the mobility shift of HspA, suggesting that HspA interacts with phycocyanin or allophycocyanin. In vitro experiments with purified phycocyanin α or β subunit and HspA are in progress to detect a direct interaction between them.
