recAProteinen

The recA protein is a crucial protein in prokaryotic DNA repair and recombination. It plays a central role in the RecBCD pathway of homologous recombination in bacteria like *Escherichia coli*. When DNA is damaged, particularly double-strand breaks, the recA protein becomes activated.

Upon activation, recA forms a nucleoprotein filament on single-stranded DNA (ssDNA) that is exposed at the break site. This filament has the remarkable ability to scan homologous DNA sequences and initiate strand invasion. This process is essential for repairing damaged DNA by using a homologous intact DNA molecule as a template.

Beyond repair, the recA protein is also involved in the SOS response, a global regulatory network that allows bacteria to survive DNA damage. Activation of recA triggers the cleavage of the LexA repressor, which in turn derepresses a wide array of genes involved in DNA repair and mutagenesis. The filament formation by recA on ssDNA is the key event that leads to this proteolytic cleavage. Its ability to bind to both ssDNA and double-stranded DNA (dsDNA) and facilitate strand exchange makes it a highly versatile and indispensable molecule for maintaining genomic integrity.