Fig. 3. Fusion pore expansion is controlled by membrane tension, distance between the membranes and line tension of the pore edge.
A. Membrane tension of 0.3mN/m is sufficient to drive fusion pore expansion for membranes (shown as light blue films) separated by ≥45nm. Proteins that mediate adhesion are shown as orange shapes. B. To drive fusion pore expansion in a tighter contact zone, the membranes have to be subjected to a higher tension. C. In the tight contact zone, accumulation of intracellular membrane-bending proteins at the rim of the pore would lower its line tension and, thus, the membrane tension required to drive the pore expansion.