In cyanobacteria Synechocystis sp. PCC6803 the light-dependent level of SppA2 protein is regulated by SppA1 peptidase

Abstract

Photosynthetic bacteria contain one or two homologues of the signal peptide peptidase A Escherichia coli, designated SppA1 and SppA2. SppA2 protein is unique for prokaryotic cells and in cyanobacterium Synechocystis sp. PCC6803 (Synechocystis) is encoded by the gene slr0021. We have established that in cyanobacteria the transcriptional and post-translational levels of SppA2 protein regulated in opposite directions depending on the light intensity. Expression analysis of slr0021 shows a pattern namely a light-induced increase of mRNA levels. Opposite to that the protein levels decrease with increase of light intensity. Later we have found that the post-translational level of SppA2 is regulated by SppA1 or a SppA1-controlled protease. Regulation of SppA2 levels appears to be light specific and is not affected by temperature stress or nitrogen starvation.