CRYSTALLIZATION AND PRELIMINARY-X-RAY DIFFRACTION STUDIES OF THE SACCHAROMYCES-CEREVISIAE PHOSPHOLIPID-TRANSFER PROTEIN SEC14P

The Saccharomyces cerevisiae phosphatidylinositol-transfer protein Sec 14p catalyzes the exchange of phosphatidylinositol or phosphatidylchol ine between membrane bilayers in vitro, and is an essential protein re quired for the budding of secretory vesicles from the yeast Golgi comp lex in vivo. At issue is the fundamental question of how the dual phos pholipid ligand specificity of Sec14p translates to in vivo function. In an attempt to determine the structural basis for how Sec14p binds e ach of its phopholipid ligands, Sec14p occupied with phosphatidylcholi ne has been purified and the complex crystallized in the presence of t he mild detergent n-octyl beta-D-glucopyranoside. The Sec14p crystals diffract to 2.7 Angstrom and belong to space group P3(1)21 or P3(2)21 with unit-cell dimensions of a = b = 88.79, c = 111.21 Angstrom, alpha = beta = 90, gamma = 120 degrees. As Sec14p exhibits significant prim ary sequence homology to mammalian retinaldehyde binding proteins and the noncatalytic domain of human MEG2 protein tyrosine phosphatase, is is anticipated that solution of the Sec14p crystal structure will pro vide new functional insights for a family of interesting proteins.