[The role of divalent cations in DNA endonucleolysis catalyzed by restrictases]

Electrophoretic analysis of products obtained after hydrolysis of phage lambda DNA by means of restrictase Pae I was carried out after preincubation of DNA or the enzyme with Mg2+ as well as after preincubation of DNA simultaneously with the enzyme and the subsequent addition of the required components into the experimental samples. The analysis showed that Mg2+ were apparently not required for the enzyme-substrate complex formation and caused destabilization of the complex. Restrictase Pae I was in active form when Mg2+ was substituted by Mn2+, Ca2+, Zn2+, Co2+ but not by Cd2+, Cu2+ or Ni2+. Experiments with o-phenanthroline showed that Zn2+ cations are of importance in catalytic activity of restrictase Pae I. Possible functions of Zn2+ in protein-nucleic acids recognition are discussed.