Figure 4. Fur protects GATC-I from methylation in vitro.

A radiolabeled PCR product corresponding to the 596-bp sci1 promoter was digested by the restriction enzymes indicated on top (no, no digestion). Upper panel, untreated PCR product; middle panel, PCR product treated with the Dam methylase; lower panel, PCR product incubated with purified Fur (20 nM) prior to Dam methylation. The sizes of the digestion products (in bp) are indicated on the left. Red and blue frames emphasize the observation that incubation with Fur did not change the digestion profiles for GATC-II (-II) and GATC-III (-III) whereas the green frame emphasize the observation that GATC-I (-I) was not methylated upon Fur binding. Schematic representations of the conclusions of the left panels are shown on right. See Figure S1 for positions of restriction sites and sizes of DNA fragments.