Figure 4.

Activity of immunoprecipitated HhaI methyltransferases. Wild-type or mutant methyltransferases were precipitated from crude extract using anti-HhaI antibodies and protein A–Sepharose beads. The immunoprecipitated proteins were assayed for methyltransferase activity using the DE81 filter binding assay, as described in Materials and Methods. The figure shows activity for the mutant methyltransferases: (A) F18W, F18C, F18H, F18S and D60P; (B) W41I, W41A and W41Y. The activity shown is percentages normalized against wild-type M.HhaI. WT stands for wild-type.