SNAPs, a family of NSF attachment proteins involved in intracellular membrane fusion in animals and yeast

TLDR

The SNAP‑NSF‑membrane complex is thought to be an early step in assembling a multisubunit fusion machine, and SNAP activity is conserved in yeast. Three SNAP proteins (α, β, γ) were purified from bovine brain; each binds NSF to Golgi membranes and is required for cisternal transport, and yeast sec17 mutants lacking SNAP activity are rescued by α‑SNAP, indicating a conserved fusion mechanism.

Abstract

Three new and likely related components of the cellular fusion machinery have been purified from bovine brain cytosol, termed α-SNAP (35 kd), β-SNAP (36 kd), and γ-SNAP (39 kd). Transport between cisternae of the Golgi complex measured in vitro requires SNAP activity during the membrane fusion stage, and each SNAP is capable of binding the general cellular fusion protein NSF to Golgi membranes. The SNAP-NSF-membrane complex may be an early stage in the assembly of a proposed multisubunit "fusion machine" on the target membrane. SNAP transport factor activity is also found in yeast. Yeast cytosol prepared from a secretion mutant defective in export from the endoplasmic reticulum (sec17) lacks SNAP activity, which can be restored in vitro by the addition of pure α-SNAP, but not β- or γ-SNAPs. These data suggest that the mechanism of action of SNAPs in membrane fusion is conserved in evolution.