In this paper we present evidence that phosphatidylinositol 4-phosphate induces curvature in biological membranes. The phase behaviour of mixtures of distearoylphosphatidylinositol 4-phosphate (DSPIP) and dioleoylphosphatidylcholine (DOPC) as a function of pressure and temperature has been studied using small-angle X-ray scattering and in the presence of biologically relevant magnesium concentrations. Our results demonstrate that at physiologically relevant concentrations (2 mol%), DSPIP is capable of inducing the formation of the inverse hexagonal phase (H-II) over a wide range of conditions. This result has implications for the structural role of phosphatidylinositol lipids in vivo.
- INOSITOL TRISPHOSPHATE
- CLATHRIN-DEPENDENT ENDOCYTOSIS