FIGURE 1.

O⁶-methyl-guanine DNA methyltransferase activity of SsOGT. A, scheme of the radioactive assay (see “Experimental Procedures” for details). B, autoradiography of the reactions with 50 ng of SsOGT, in the presence of a radiolabeled 38-bp dsDNA containing or not a single methyl-guanine (ds-UP^m and ds-UP, respectively). Reactions were incubated at 70 °C for 1 h; then, 5.0 units of MboI endonuclease were added where indicated, and incubation continued at 37 °C (see Table 1 and “Experimental Procedures” for details).