Crystallization and preliminary X-ray diffraction analysis of BcOMT2 from Bacillus cereus: a family of O-methyltransferase.

O-Methyltransferases (OMTs), one of the ubiquitous enzymes in plants, bacteria, and humans, catalyze a methyl-transfer reaction using S-adenosylmethionine and a wide range of phenolics as a methyl donor and acceptor, respectively. Substrates for most bacterial OMTs have largely remained elusive, but recent investigation using BcOMT2, an OMT from Bacillus cereus, suggested that ortho-dihydroxyflavonoids could serve as substrates. To elucidate the functional and structural features of BcOMT2, we expressed, and purified BcOMT2, and crystallized an apoenzyme and its ternary complex in the presence of a flavonoid and S-adenosylhomocysteine. Each crystal diffracted to 1.8 angstroms with its space group of C2 and P2(1)2(1)2(1), respectively. Structural analysis of apo-BcOMT2 and its ternary complex will provide the structural basis of methyltransfer onto (iso)flavonoids in a regiospecific manner.