Crystal structure of the Saccharomyces cerevisiaephosphatidylinositol-transfer protein.
Nature. 1998; 391: 506-10
Display abstract
The yeast phosphatidylinositol-transfer protein (Sec14) catalyses exchangeof phosphatidylinositol and phosphatidylcholine between membrane bilayersin vitro. In vivo, Sec14 activity is essential for vesicle budding fromthe Golgi complex. Here we report a three-dimensional structure for Sec14at 2.5 A resolution. Sec14 consists of twelve alpha-helices, sixbeta-strands, eight 3(10)-helices and has two distinct domains. Thecarboxy-terminal domain forms a hydrophobic pocket which, in the crystalstructure, is occupied by two molecules of n-octyl-beta-D-glucopyranosideand represents the phospholipid-binding domain. This pocket is reinforcedby a string motif whose disruption in a sec14 temperature-sensitive mutantresults in destabilization of the phospholipid-binding domain. Finally, wehave identified an unusual surface helix that may play a critical role indriving Sec14-mediated phospholipid exchange. From this structure, wederive the first molecular clues into how a phosphatidylinositol-transferprotein functions.
Dimeric Sec14 family homolog 3 from Saccharomyces cerevisiae presents some novel features of structure that lead to a surprising "dimer-monomer" state change induced by substrate binding