Proteolytic activation of UmuD and MucA proteins for SOS mutagenesis

SOS mutagenesis in Escherichia coli requires the functions of the umuD, C genes, or their functional analogues mucA, B derived from a plasmid pKM101, and the recA gene. However, mere derepression of these SOS genes does not increase the ability of the cell to perform mutagenesis. Activation of RecA protein to a form (RecA*) that mediates cleavage of the LexA repressor is required for mutagenesis. We present evidence that UmuD and MucA are proteolytically processed by RecA* and that the processed products are the active forms involved in mutagenesis.