Crystallization and preliminary X-ray diffraction study of BchU, a methyltransferase from Chlorobium tepidum involved in bacteriochlorophyll c biosynthesis

The S-adenosylmethionine-dependent methyltransferase BchU is an enzyme involved in the bacteriochlorophyll c biosynthetic pathway and catalyzes methylation at the C-20 position of the chlorin moiety. Recombinant Chlorobium tepidum BchU overproduced in Escherichia coli was purified and crystallized by the hanging-drop vapour-diffusion method using ammonium sulfate as a precipitant. The crystals belonged to the hexagonal space group P6(1)22 or P6(5)22, with unit-cell parameters a = b = 81.5, c = 250.7 A. A native data set was collected to 2.27 A resolution using synchrotron radiation at SPring-8.