Fig. 1.

The structure of the inositide lipid group. All combinations and permutations of phosphates at R¹, R² and R³ have been found in vivo, with phosphatidylinositol-4,5-bisphosphate (PI-4,5-P ₂; R² and R³ = -PO₃H⁻, R¹ = H), phosphatidylinositol 4-phosphate (PI-4-P; R² = -PO₃H⁻, R¹ and R³ = H), and phosphatidylinositol (PI, R¹, R² and R³ = H) forming the bulk of the mass of inositides under typical physiological conditions [2, 3]