Immunological quantification of RecA protein in cell extracts of E. coli after exposure to chemical mutagens or UV radiation.

Increased synthesis of RecA protein is induced in E. coli cells after their damage, the rate of synthesis being dependent on the extent of DNA alterations. The level of the RecA protein was determined in E. coli cell extracts after damage induced by NQO, MNNG, MMC, NAL or UV radiation, using competitive enzyme-linked immunosorbent assay (ELISA). Purified E. coli RecA protein and rabbit monospecific polyclonal antibodies against it were prepared for the quantitative assay. The level of the RecA protein was increased after treatment with all mutagens. Contrary to other induced proteins, the synthesis of the RecA protein increased within 30 min after damage with UV radiation at a relatively slow rate. The ELISA method made it possible to determine 0.5-50 ng of the RecA protein in bacterial extracts. The method can be employed as an auxiliary test for DNA damage determination and also in studied concerning the role of the RecA protein in repair processes.