MM HEPES-KOH, pH 7.4, 75 mM NaCl, and 10 glycerol). Anisotropy measurements (excitation wavelength, 494 nm; emission wavelength, 524 nm) were recorded at 22 using a FluoroLog spectrofluorometer (Horiba Scientific) following successive additions of purified Tric1SAM (wild type or variants; concentration ranging from 0 to 1,350 nM). The binding reactions were allowed to stabilize for 200 s before