Crystallization and preliminary X-ray analysis of native and recombinant human bile-salt dependent lipase: strategies for improvement of diffraction quality

Human bile-salt dependent lipase (BSDL), secreted into both the digestive tract and human milk, is integral to the effective absorption of dietary lipids. In attempts to obtain crystals suitable for high-resolution X-ray crystallographic studies, various forms of the enzyme have been crystallized, including native and desialidated human milk BSDL and both intact recombinant BSDL and a truncated form lacking the heavily glycosylated C-terminal repeat region. Trigonal crystals of native BSDL, with unit-cell parameters a = b = 90.0, c = 156.1 Å, were obtained using 15-20%(w/v) PEG 8000 as precipitant. These crystals diffract to 3.5 Å along the unique axis, but to only 5-7 Å in orthogonal directions. Crystals of recombinant truncated BSDL grown from 15-20%(w/v) PEG 6000 are orthorhombic, space group P2₁2₁2₁, with unit-cell parameters a = 59.2, b = 90.0, c = 107.7 Å, and diffract to 2.6 Å resolution. These are suitable for structural analysis by X-ray crystallography.