RESUMO
The initial stage of membrane fusion under the action of fusion proteins transmitting force to the membrane is considered in the work. Protein inclusions in the membrane create a highly curved bulge, which facilitates fusion of contacting membrane monolayers. Membrane is considered as a liquid-crystal medium subjected to elastic deformations. Deformations of splay and tilt are taken into account and energy is calculated to the second order on these deformations. Protein complexes are modeled as rigid tilted rings embedded into the fusing membranes. The energy needed to locally bring membranes together under the action of proteins is calculated. The dependence of the membrane energy on a protein ring radius is shown to be minimum. It means that membrane deformations stabilize the radius of the protein cluster. The main characteristics of the system, such as equilibrium radius of the protein complex and the minimal energy needed to accomplish the first stage of the fusion, are calculated.
