Pteridine glycosyltransferase from Chlorobium tepidum: crystallization and X-ray analysis

The pteridine glycosyltransferase (PGT) found in Chlorobium tepidum (CtPGT) catalyzes the conversion of l-threo-tetrahydrobiopterin to 1-O-(l-threo-biopterin-2′-yl)-β-N-acetylglucosamine using UDP-N-acetylglucosamine. The gene for CtPGT was cloned, and selenomethionine-derivatized protein was overexpressed and purified using various chromatographic techniques. The protein was crystallized by the hanging-drop vapour-diffusion method using 0.24 M triammonium citrate pH 7.0, 14%(w/v) PEG 3350 as a reservoir solution. Multiple-wavelength anomalous diffraction data were collected to 2.15 A resolution from a single CtPGT crystal. The crystal belonged to the monoclinic space group C2, with unit-cell parameters a = 189.61, b = 79.98, c = 105.92 A, β = 120.5°.