Anàlisi de la variabilitat de la caixa SOS en el Domini Bacteria

The bacterial SOS system is a cellular network whose genes encoded a pool of proteins involved in DNA repair. This system is negatively regulated by the LexA protein, which binds to a specific sequence called as the SOS box. The only three seuqences of SOS boxes known so far are the CTGTN\sub 8\nosub ACAG and GAACN\sub 4\nosub GTTC palindromes and the GTTCN\sub 7\nosub GTTC direct repeat, which have been identified in E. coli, B. subtilis and Alpha Class of the Proteobacteria, respectively. Nevertheless, TBLASTN analysis carried out by our group have pointed out that other LexA proteins belonging to several phylogenetic groups and able to bind SOS boxes different to those three above cited must exit. The main goal of this project is the isolation of 11 lexA genes from representative members of 7 phyla of the Bacteria Domain to identify their SOS boxes. To achieve this objective, LexA proteins encoded by these genes will be expressed and purified from recombinant E. coli cells to be used in mobility shift and footprint assays with their respective recA and lexA promoters. After identification of different SOS boxes, a comparative study among them will be performed. Further, with the aim to analyse the evolution of the number and the kind of SOS genes in the Bacteria Domain, a preliminary analysis of their presence through the appropiate software will be performed in genomes of bacterial species which they are from