SNARE protein analog-mediated membrane fusion.

Fusion of lipid membranes to form a single bilayer is an essential process for life and provides important biological functions including neurotransmitter release. Membrane fusion proteins facilitate approximation of interacting membranes to overcome the energy barrier. In case of synaptic transmission, proteins involved are known as soluble N-ethylmaleimide-sensitive-factor attachment receptor (SNARE) proteins. The SNAREs from synaptic vesicles interact with the SNAREs from the target membrane to form a coiled-coil bundle of four helices, thus pulling the membranes tightly together and initiating fusion. However, it remains unclear how these proteins function at molecular level. Natural systems are often too complex to obtain unambiguous results. Simple model systems mimicking natural proteins in synthetic lipid bilayers are powerful tools for obtaining insights into this essential biological process. An important advantage of such systems is their well-defined composition, which can be systematically varied in order to fully understand events at molecular level. In this review, selected model systems are presented based upon specific interactions between recognition units embedded in separate lipid bilayers mimicking native SNARE protein-mediated membrane fusion.