Figure 4. Interactions of SNAREs with tethering factors via their N-terminal domains, showing various levels of regulation.

SNAREs may switch from an inactive closed conformation, with the N-terminal domain binding to the SNARE motif, to an active open conformation. This transition may be promoted by SM proteins, or in some cases also by posttranslational modifications. In the open conformation, the N-terminal domains may bind to tethering factors or to other adaptors in a mutually exclusive fashion. In some cases, association with another SNARE is required for the specific recruitment of a tethering factor. See text for details.