Fig. 1.

Domain and loop motions in M.HhaI. The backbone atoms of the large domain (residues 1–190 and 304–327) for nine ternary (with various forms of DNA and cofactor) and two binary (with AdoMet) structures were superimposed onto the 6MHT structure. The DNA and cofactor are shown as gray sticks with the open group of M.HhaI structures (5MHT, 6MHT, 7MHT, 8MHT, 9MHT, and 10MH) as green and a more closed group (1MHT, 3MHT, and 4MHT) as blue. The binary complexes shown in red (1HMY and 2HMY) adopt an even more open conformation. The catalytic loop (residues 80–99) of the binary complexes moves up to 26 Å from its position in the ternary complexes and was left out of the superimpositions. These superimpositions reveal the changes in domain orientation and catalytic loop conformation upon substrate binding.