Formation of the layer of influenza A virus M1 matrix protein on lipid membranes at pH 7.0

Abstract

The kinetics of interaction of influenza A virus M1 matrix protein with hydrophilic polymer-supported lipid bilayers formed by 1,2-diphytanoyl-sn-glycero-3-phosphocholine and 1,2-diphytanoyl-sn-glycerophospho-l-serine at pH 7.0 was studied by surface plasmon resonance spectroscopy. The M1 protein was shown to bind to the lipid bilayer almost irreversibly to form a monolayer; this is in line with the key function of the M1 protein, that is, formation of the protein envelope of the virion. An increase in the percentage of negatively charged lipids from 0 to 30% leads to a considerable increase in the protein monolayer density and a several-fold increase in the binding constant (K_a) of the M1 protein with the lipid bilayer up to (3.60±0.11)·10⁸ L mol^–1. The negatively charged lipids in the bilayer appear to promote the manifestation of anisotropic properties of the M1 protein, which enable the protein to form reversible non-monolayer structures on the surface. The M1—M1 interaction was found to be reversible and to be characterized by the binding constant K_a = (6.3±0.1)·10⁷ L mol^–1.