Structure of a binary complex of HhaI methyltransferase with S-adenosyl-L-methionine formed in the presence of a short non-specific DNA oligonucleotide
M. O'Gara et al., Structure of a binary complex of HhaI methyltransferase with S-adenosyl-L-methionine formed in the presence of a short non-specific DNA oligonucleotide, J MOL BIOL, 287(2), 1999, pp. 201-209
We have determined a structure for a complex formed between HhaI methyltran
sferase (M.HhaI) and S-adenosyl-L-methionine (AdoMet) in the presence of a
non-specific short oligonucleotide. M.HhaI binds to the non-specific short
oligonucleotides in solution. Although no DNA is incorporated in the crysta
l, AdoMet binds in a primed orientation, identical with that observed in th
e ternary complex of the enzyme, cognate DNA, and AdoMet or S-adenosyl-L-ho
mocysteine (AdoHcy). This orientation differs from the previously observed
unprimed orientation in the M.HhaI-AdoMet binary complex, where the S+-CH3
unit of AdoMet is protected by a favorable cation-pi interaction with Trp41
. The structure suggests that the presence of DNA can guide AdoMet into the
primed orientation. These results shed new light on the proposed ordered m
echanism of binding and explains the stable association between AdoMet and
M.HhaI. (C) 1999 Academic Press.