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 t ract and human milk, is integral to the effective absorption of dietary lip ids. In attempts to obtain crystals suitable for high-resolution X-ray crys tallographic studies, various forms of the enzyme have been crystallized, i ncluding native and desialidated human milk BSDL and both intact recombinan t BSDL and a truncated form lacking the heavily glycosylated C-terminal rep eat region. Trigonal crystals of native BSDL, with unit-cell parameters a = b = 90.0, c = 156.1 Angstrom, were obtained using 15-20% (w/v) PEG 8000 as precipitant. These crystals diffract to 3.5 Angstrom along the unique axis , but to only 5-7 Angstrom in orthogonal directions. Crystals of recombinan t truncated BSDL grown from 15-20%(w/v) PEG 6000 are orthorhombic, space gr oup P2(1)2(1)2(1), with unit-cell parameters a = 59.2, b = 90.0, c = 107.7 Angstrom, and diffract to 2.6 Angstrom resolution. These are suitable for s tructural analysis by X-ray crystallography.