Crystallization and preliminary X-ray diffraction analysis of Sfh3, a member of the Sec14 protein superfamily.

Sec14 is the major phosphatidylinositol (PtdIns)/phosphatidylcholine (PtdCho) transfer protein in the yeast Saccharomyces cerevisiae and is the founding member of the Sec14 protein superfamily. Recent functional data suggest that Sec14 functions as a nanoreactor for PtdCho-regulated presentation of PtdIns to PtdIns kinase to affect membrane trafficking. Extrapolation of this concept to other members of the Sec14 superfamily suggests a mechanism by which a comprehensive cohort of Sec14-like nanoreactors sense correspondingly diverse pools of lipid metabolites. In turn, metabolic information is translated to signaling circuits driven by phosphoinositide metabolism. Sfh3, one of five Sec14 homologs in yeast, exhibits several interesting functional features, including its unique localization to lipid particles and microsomes. This localization forecasts novel regulatory interfaces between neutral lipid metabolism and phosphoinositide signaling. To launch a detailed structural and functional characterization of Sfh3, the recombinant protein was purified to homogeneity, diffraction-quality crystals were produced and a native X-ray data set was collected to 2.2 Å resolution. To aid in phasing, SAD X-ray diffraction data were collected to 1.93 Å resolution from an SeMet-labeled crystal at the Southeast Regional Collaborative Access Team at the Advanced Photon Source. Here, the cloning and purification of Sfh3 and the preliminary diffraction of Sfh3 crystals are reported, enabling structural analyses that are expected to reveal novel principles governing ligand binding and functional specificity for Sec14-superfamily proteins.