Membrane fusion pores belong to three families

During exocytosis, membrane fusion generates a fusion pore through which neurotransmitters, hormones or other bioactive molecules are released. Fusion pores regulate release rates, filter by molecular size and determine the fate of fused vesicles (plasma membrane merging, growth, or pinching off). Despite its key role, the structure and energetics of fusion pores are not established. Here we report exact results. We find there are three pore families with different shapes and size (Jia et al., 2021), and we find the energy landscape suggests dilation of a small nascent pore, widely observed in amperometry as the “pre spike foot to spike” transition (Chow et al., 1992), is a transition between two families.