[Isoelectric focusing of DNA-methylases from Shigella sonnei 47].

Fractionation of bacterial methylases was studied by means of isoelectrofocusing technique. The method exhibited high accuracy, efficiency and reproducibility in studies of methylases from Shigella sonnei 47. High column capacity and distinct focusing effect increased the experimental advantages of work with various amounts of protein as compared with ion exchange chromatography. By means of the isoelectrofocusing technique three methylases were detected in the strain S. s o n n e i 47, which were dissimilar in their isoelectric points at pH 6.5, 8.4 and 9.8. These findings indicate the heterogeneous pattern of enzyme methylation in the strain studied. Complete removing of endogenous DNA was the main precondition for correct fractionation of methylases by means of the isoelectrofocusing technique. A procedure is described for purification of S. s o n n e i 47 methylases from traces of endogenous DNA by affinity chromatography on heparin-Sepharose.