To try out their technique, the scientists synthesized molecules that mimicked AdoMet, but had chemical groups with longer carbon chains in the position where the methyl group was usually located. The enzymes were able to grab the bulkier group and transfer it to DNA. Since the family of DNA methyltransferases includes enzymes capable of recognizing over 200 distinct sequences, this new approach provided an unprecedented ability to manipulate DNA experimentally.
To demonstrate the technique's potential to alter DNA function, the researchers modified DNA in a position that blocked another enzyme's ability to snip the molecule at its target site. "No one has really thought about possible applications [of this] before because no one thought it was possible,' said Klimasauskas. He predicts that DNA methyltranferases will become a standard laboratory tool like restriction endonucleases.
Earlier studies had suggested that the transfer of chemical groups larger than a methyl group would not be possible, in part because replacing AdoMet's methyl group lowered the chemical reactivity of the compound. To overcome this problem, the authors took some tips from organic chemistry textbooks and stabilized the transfer with a multiple carbon bond.
"It turned out that our first bet, a double or triple carbon-carbon bond, placed next to the transferable carbon unit, helped to alleviate the problems that had plagued the reaction in previous studies," Klimasauskas said. He likened the chemical reaction to a mechanical spring, explaining that the chemical energy trapped in AdoMet is sufficient to deliver a small methyl group to its target compound. But delivering a larger compound required an auxiliary "spring" to ensure it would reach the target. So, he said, "chemical thinking" helped resolve the problematic enzymatic reaction.
"By demonstrating the transfer of carbon chains as long as 4
Source:Howard Hughes Medical Institute