Figure 3.

Fluorescence emission spectra (excitation at 310 nm) of 2-AP incorporated in duplex 1 (i.e. having 2-AP at the position of CH₃ addition, Table 1) with a mutant of M.EcoKI. Spectrum 1, DNA duplex 1 alone; spectrum 2, DNA duplex 1 with M.EcoKI F269Y mutant; spectrum 3, complex of DNA duplex 1, M.EcoKI F269Y mutant and AdoMet taken after a 15 min incubation period with AdoMet. In these spectra, the buffer background has been subtracted. Although the mutant protein can bind AdoMet and retains some methyltransferase activity, no 2-AP* is formed.