Abstract
LexA is a repressor involved in SOS response, which has been extensively studied in Escherichia coli. Although many cyanobacteria have a lexA-like gene in genome, little is known about the SOS response in cyanobacteria. We already reported by DNA microarray analysis that LexA-like Sll1626 in Synechocystis sp. PCC 6803 was involved in transcriptional regulation of pil genes but not the SOS-related genes. In this work, we expressed and purified LexA homologs of Synechocystis (Sll1626) and Anabaena sp. PCC 7120 (Alr4908). When Anabaena Alr4908 was incubated, autocleavage products increased with time, especially at high pH, in consistent with the findings on the E. coli LexA. Meanwhile, Synechocystis Sll1626 did not produce any cleavage products. These results suggest that the LexA-like Sll1626 of Synechocystis, which is functional as a repressor, is regulated by yet unknown mechanism rather than the SOS-responsive manner.
