Figure 3.

Limited tryptic proteolysis of SimR in the presence or absence of DNA. SimR was incubated either alone or with the O_X operator DNA duplexes indicated, before the addition of trypsin. Note that the 15-mer DNA duplex does not bind SimR (Supplementary Figure S5A). After SDS–PAGE, SimR species were visualized by Coomassie blue staining. The major product of tryptic digestion (arrowed) was shown by Edman sequencing to have an N-terminus corresponding to Ser20 or Ser23 of wild-type SimR.