HhaI methyltransferase flips its target base out of the DNA helix.
Klimasauskas, S., Kumar, S., Roberts, R.J., Cheng, X.(1994) Cell 76: 357-369
- PubMed: 8293469 
- DOI: 10.1016/0092-8674(94)90342-5
- Primary Citation of Related Structures:  
1MHT - PubMed Abstract: 
The crystal structure has been determined at 2.8 A resolution for a chemically-trapped covalent reaction intermediate between the HhaI DNA cytosine-5-methyltransferase, S-adenosyl-L-homocysteine, and a duplex 13-mer DNA oligonucleotide containing methylated 5-fluorocytosine at its target ...