nonSNARE

Nonsnare is an informal term occasionally used in cell biology to refer to proteins or molecules that do not function as SNAREs in vesicle fusion. SNARE proteins (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) are the core components that mediate membrane fusion by forming a SNARE complex between vesicles and target membranes. The word nonsnare is not a formal scientific classification; it is often used to distinguish the SNARE machinery from other proteins involved in membrane trafficking.

In this usage, nonsnare encompasses a variety of non-SNARE components that influence vesicle fusion and trafficking. Examples include Rab family GTPases that regulate vesicle targeting, tethering factors that mediate initial vesicle docking, and SM proteins such as Sec1/Munc18 that regulate SNARE complex assembly. Enzymes like NSF and its adaptor α-SNAP, which act to disassemble SNARE complexes after fusion, are also non-SNARE elements. Because many proteins contribute to fusion indirectly or regulate SNARE activity rather than forming part of the SNARE bundle itself, the term nonsnare serves as a broad descriptive label rather than a precise functional category.

Usage of the term is limited and not universally adopted in the literature. When discussing membrane trafficking, authors typically name the specific proteins involved or refer to “non-SNARE components” rather than using the umbrella term nonsnare. See also SNARE protein, vesicle trafficking, tethering complex, Rab GTPase.