Gene clpP2Encoding Peptidase in the Synechocystissp. PCC 6803 Cyanobacterium Controls Cell Sensitivity to Photoinhibition

A homozygous insertion mutant with the inactivated clpP2gene, which encodes the proteolytic subunit of ATP-dependent peptidase, was obtained in the unicellular cyanobacterium Synechocystissp. PCC 6803. The mutant cannot grow under photoautotrophic conditions, but cells grown under heterotrophic conditions in a glucose-containing medium have active photosystems Iand II(PS Iand PS II). The loss of capacity for photoautotrophic growth is determined by a high sensitivity of mutant cells to the inactivating effect of light. Their incubation under light with an intensity above 10 μE m–2s–1inhibits cell growth in culture and causes degradation of photosynthetic pigments. It is proposed that the ClpP2 peptidase is involved in the protection of Synechocystis6803 cells from photoinhibition.