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Mol Cell. 2012 Aug 10;47(3):339-48. doi: 10.1016/j.molcel.2012.05.027. Epub 2012 Jun 14.

Two-site recognition of phosphatidylinositol 3-phosphate by PROPPINs in autophagy.

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Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.


Macroautophagy is essential to cell survival during starvation and proceeds by the growth of a double-membraned phagophore, which engulfs cytosol and other substrates. The synthesis and recognition of the lipid phosphatidylinositol 3-phosphate, PI(3)P, is essential for autophagy. The key autophagic PI(3)P sensors, which are conserved from yeast to humans, belong to the PROPPIN family. Here we report the crystal structure of the yeast PROPPIN Hsv2. The structure consists of a seven-bladed β-propeller and, unexpectedly, contains two pseudo-equivalent PI(3)P binding sites on blades 5 and 6. These two sites both contribute to membrane binding in vitro and are collectively required for full autophagic function in yeast. These sites function in concert with membrane binding by a hydrophobic loop in blade 6, explaining the specificity of the PROPPINs for membrane-bound PI(3)P. These observations thus provide a structural and mechanistic framework for one of the conserved central molecular recognition events in autophagy.

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