Polyunsaturated phosphatidylinositol and diacylglycerol substantially modify the fluidity and polymorphism of biomembranes: A solid-state deuterium NMR study

One of the main biological systems that can be used as a model for studying the molecular mechanisms involved in membrane fusion is the formation of the nuclear envelope (NE). NE assembly to form the male pronucleus at fertilization occurs by binding of NE membrane precursor vesicles to chromatin and their fusion. MV₁ is an NE precursor vesicle population of low density, highly enriched in {18:0/20:4}PI. The modification of {18:0/20:4}PI to {18:0/20:4}DAG leads to NE formation, and the depletion of MV₁ from the total membrane precursors results in the inhibition of NE assembly. Here we show by ²H NMR studies of various physiologically relevant model membranes made of {18:0/20:4}PI, {18:0/20:4}DAG, and saturated and unsaturated PC that membranes of composition similar to MV₁ exhibit dramatically enhanced fluidity and non-lamellar structures, thus providing a possible explanation for the essential role of MV₁ and the modification of PI to DAG in membrane precursor vesicles during NE assembly.