Western blot analysis of RecA protein in crude extract of E. coli Lane 1, Purified RecA 8 ng. Lane 2, Wild type. Lane 3, ⊿recA mutant. Lane 4, ⊿lexA mutant (SOS genes overexpressed). Antibody used at 1/3,000 dilution. Cell extracts, 2 μg

Immunoprecipitation of RecA protein from crude extract of E. coli cells. Antibody 2 μg was adsorbed to proteinA magnetic beads to precipitate RecA protein from supernatant of sonic disrupted E. coli cells. The precipitate was analyzed by western blot.