A mathematical model for protein-induced lipid vesicle leakage: interaction of the intermediate filament protein vimentin and its isolated N-terminus with phosphatidylinositol vesicles.

A mathematical model was developed to analyze the leakage of phosphatidylinositol small unilamellar vesicles induced by the intermediate filament protein vimentin and its isolated N-terminal polypeptide. This model describes the kinetic and steady-state characteristics of this vesicle leakage as a direct action of protein on the lipid bilayer. Moreover, qualitative information at the molecular level can be deduced about protein-protein or protein-lipid interactions from the derived initial rate of vesicle leakage and the value of vesicle leakage at steady-state condition as a function of the protein concentration. Additionally, quantitative data on the inhibitory effect of various substances (here Ca2+ or Mg2+) can also be derived. This approach offers a possibility to compare interactions occurring within different protein-lipid systems by determining the characteristic parameters for the respective kinetic and steady-state conditions.