Abstract
We have shown the heat-induced photobleaching of phycobilisomes in cyanobacteria. Consitituve expression of HspA in Synechococcus protected phycocyanin from losing its light-harvesting property. The present study aims to reveal the mechanism of the bleaching and how HspA can protect phycocyanin from the bleaching.
Cell extracts were prepared from the reference strain, Synechococcus strain ECT, and the HspA expressing strain ECT16-1 after a heat shock. The former strain showed the phycocyanin bleaching, while the latter one did not. Phycobilisome of the ECT cell was much more prone to heat-denaturation than that of the ECT16-1 cell. Purified phycobilisome was incubated in the presence or absence of HspA at 50oC in the presence of H2O2. This treatment resulted in the protein aggregation and phycocyanin bleaching. However, addition of HspA suppressed the denaturation. Studies on a specific interaction between HspA and a phycobilisome component are in progress.
