Prefusion

Prefusion refers to the state of a membrane protein before it has undergone its final conformational change to become fusion-competent. This is a critical stage in processes involving membrane fusion, such as viral entry into host cells or the fusion of organelles within a cell. In this prefusion conformation, the protein typically adopts a relatively stable structure that is distinct from its postfusion state. This prefusion state is often characterized by exposed regions that will later be involved in interacting with a target membrane or in undergoing significant structural rearrangements.

The transition from the prefusion state to the postfusion state is usually triggered by specific environmental cues. These triggers can include changes in pH, the binding of a ligand, or interactions with other molecules. Once triggered, the protein undergoes a series of conformational changes that ultimately lead to the merging of two lipid bilayers. Understanding the prefusion state is important for studying the mechanisms of membrane fusion and for developing therapeutic strategies that target these processes. For instance, inhibiting the transition from the prefusion to the postfusion state can prevent viral infection or disrupt unwanted cellular fusion events. The specific structure of the prefusion state can vary significantly among different fusion proteins, reflecting the diverse mechanisms by which fusion is achieved.