MchAI and MchAII, two class-II restriction endonucleases from Mycobacterium chelonei

We have purified and characterized two class-II restriction endonucleases from the saprophyte Mycobacterium chelonei AMB 82. MchAI was an isoschizomer of NotI recognizing and cleaving at 5'-GC/GGCCGC. MchAI did not require Triton X-100 for activity and was fully active at concentrations over 10-200 mM KCl and MgCl2. MchAII was an isoschizomer of HaeIII recognizing and cleaving at 5'-GG/CC. MchAII was active in 10 mM Tris.HCl pH 8.0 containing MgCl2 at 10-200 mM, was strongly inhibited by NaCl at concentrations higher than 10 mM and was inactive at KCl concentrations lower than 250 mM.