Membrane fusion reaction: A theory

A unitary theory of membrane fusion is proposed on the basis of similarities between events in cell fusion and the fusion of subcellular membrane systems. Particular emphasis is placed on the role of Ca²⁺, ATP and membrane-associated ATPase enzyme systems in regulating the membrane changes responsible for fusion. The membrane fusion reaction is considered in four stages: membrane contact; induction; fusion; and stabilization. It is suggested that under the appropriate conditions changes in the electrostatic potential created by the closed approximation of membranes (stage one) will induce the membrane changes required for the remaining three stages. Various factors influencing each stage of the membrane fusion reaction are considered in detail. The significance of membrane fusion in cell biology and objections to existing theories of fusion are discussed briefly.