Figure 5.
Visualization of processive DNA methylation by CcrM. (A) The increase in full-length N660/66-mer indicates that both sites are resistant to HindII digestion as a result of processive methylation. The majority of N660/66-mer is not utilized by CcrM and is therefore susceptible to restriction digestion by HindII. Unreacted N660/66-mer is cleaved into several distinct smaller DNA fragments, although only the largest of these fragments (≈52-mer) is shown for convenience. (B) Addition of a molar excess (10 μM) of N623/30AP-mer does not alter the production of full-length N660/66-mer, indicating that CcrM processively methylates DNA under physiological conditions.