The isolation and partial characterization of a new restriction endonuclease from Providencia stuartii

We describe the isolation of a new class 2 restriction endonuclease from Providencia stuartii 164. Using the procedure of osmotic shock treatment, we have partially purified this enzyme (Pst 1) and have begun preliminary work to characterize its specificity and requirements. Pst 1 requires Mg++ as the only cofactor and produces more than 18 cleavages in wild type lambda. We have determined the location of 7 of these cleavages by the use of deletion and insertion mutants of lambda.