Angle and locus of the bend induced by the MspI DNA methyltransferase in a sequence-specific complex with DNA

Bending of DNA induced by M.MspI, one of the m5C-DNA methyltransferases, has been investigated using circular permutation analysis. The M.MspI MTase induced sharp bends in DNA containing its recognition sequence 5'-CCGG-3' which was estimated to be 142 +/- 4 degrees and 132 +/- 4 degrees for circularly permuted DNA fragments of 127 and 1459 bp respectively. The bend centre was found to be asymmetric with respect to the CCGG sequence and appeared to exclude the 'target cytosine'. An estimate of similar to 15 kcal/mol was obtained for the free energy associated with M.MspI-induced DNA bending.