Production of R.EcoO109I and M.EcoO109I in E.coli cells carrying the wild-type and mutant ecoO109IC. Escherichia coli HB101 cells carrying p184CRM (lanes 1 and 2), p184dCRM (lanes 3 and 4), and p184intCRM (lanes 5 and 6) were transformed with pBSCEcoO109I (lanes 2, 4 and 6) or not (lanes 1, 3 and 5), and then cultured at 37°C in LB broth containing 1 mM IPTG. Cell-free extracts prepared from recombinant E.coli HB101 cells were separated by 0.1% SDS–15% PAGE (A), and then analyzed by western blotting with antibodies raised against M.EcoO109I (B) and R.EcoO109I (C), respectively. The positions of molecular mass standards (Mr) are indicated (in kDa) on the left. Lanes 7 and 8 show purified M.EcoO109I and R.EcoO109I, respectively.