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Phosphatidylinositol polyphosphates: ionization constants in fluid phosphatidylcholine model membranes
Author(s) -
Kooijman Edgar Eduard,
Gangoda Mahinda,
Kumar Satyendra,
Gericke Arne
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.lb274
Subject(s) - phosphatidylinositol , chemistry , biophysics , membrane , phosphatidylcholine , membrane biology , nuclear magnetic resonance spectroscopy , signal transduction , biochemistry , phospholipid , stereochemistry , biology
Phosphatidylinositol polyphosphates (PIPs) are only a minor pool of membrane phospholipids but are involved in many intracellular signaling processes including membrane trafficking, cytoskeleton remodeling, receptor signal transduction and nuclear events. Phosphoinositide properties are largely determined by the characteristics of their headgroup, which at physiological pH is highly charged but also capable of forming hydrogen bonds. Many proteins have developed special binding domains that facilitate specific interaction, while other proteins interact with phosphoinositides via non‐specific electrostatics. Despite its importance, only limited information is available about the ionization properties of phosphoinositides. We have investigated the pH dependent ionization behavior of all three naturally occurring phosphatidylinositol bisphosphates as well as of phosphatidylinositol‐3,4,5‐trisphosphate in mixed multi‐lamellar phosphoinositide/phosphatidylcholine vesicles using magic angle spinning 31 P‐NMR spectroscopy. Aside from the detailed pH dependent titration behavior, the current study also provides compelling evidence for mutual PIP 2 interaction without the presence of cationic proteins. The ionization behaviors of these PIPs solve several historical contradictions and will have important implications for the physiological processes in which they are involved.