Yeast Sec14-like phosphatidylinositol transfer proteins (PITPs) contain a hydrophobic cavity capable of accepting a single molecule of phosphatidylinositol (PI) or another molecule in a mutually exclusive manner. We report here that two yeast Sec14 family PITPs, Pdr16p (Sfh3p) and Pdr17p (Sfh4p), possess high-affinity binding and transfer towards lanosterol. To our knowledge, this is the first identification of lanosterol transfer proteins. In addition, a pdr16Δpdr17Δ double mutant had a significantly increased level of cellular lanosterol compared with the corresponding wild-type. Based on the lipid profiles of wild-type and pdr16Δpdr17Δ cells grown in aerobic and anaerobic conditions, we suggest that PI-lanosterol transfer proteins are important predominantly for the optimal functioning of the post-lanosterol part of sterol biosynthesis.
Keywords: Saccharomyces cerevisiae; PITP; azol; cholesterol; ergosterol; lanosterol; lipid binding; phosphatidylinositol transfer.
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