Abstract
It has been reported that several uncharacterized proteins were co-purified with PSII complex from Synechocystis sp. PCC 6803. Among them, Sll1252 is conserved among all the photosynthetic organisms, including cyanobacteria and plants, suggesting that it might have important functions.
In order to elucidate the role of Sll1252, we disrupted the gene in Synechocystis. Although the Sll1252 mutant grew under low-light conditions, it could not grow at high-light conditions and the cells were severely photodamaged. The activity of PSII determined with PBQ as an electron acceptor, and the rate of respiration in the mutant were similar to those in wild-type cells. However, the activity of net photosynthesis, from H2O to CO2, was drastically dropped in the mutant. Profiles of transcriptome in the mutant cells were similar to those in cells treated with DBMIB. The redox state of PQ-pool in the mutant was more reduced than that in wild-type cells. A doubling in copy number of the sll1252 gene increased the net photosynthetic activity, but did not alter the respiration rate. These results suggested that Sll1252 might be involved in the activity of photophosphorylation.
