Purification and characterization of recA protein from salmonella typhimurium.

recA protein was purified to homogeneity from Salmonella typhimurium TA98 strain after induction of the cells by nalidixic acid. The purification was monitored with a radioimmune assay and involved a specific elution of the protein by ATP from a single-stranded DNA-cellulose column. From 240 liters of cell culture we obtained 40 mg of recA protein which was more than 98% pure. This protein exhibited the same molecular weight as measured on sodium dodecyl sulfate-polyacrylamide gel and the same isoelectric point as the Escherichia coli recA protein purified by a similar procedure. In addition, the S. typhimurium recA protein is endowed with a single-stranded DNA-dependent ATPase activity and cleaves the phage lambda repressor in vitro at the same rate as E. coli recA protein and with the same qualitative requirements. However, peptide mapping with the Staphylococcus aureus V8 protease and cross-reaction with heterologous antibodies show that these two proteins are slightly different.