The process of vesicular membrane fusion in eukaryotic cells depends on a conserved fusion machinery called SNARE (soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptors). In the process of vesicle docking, proteins present on the vesicle (v-SNARE) have to bind to their counterpart on the target membrane (t-SNARE) to form a core complex that can then recruit the soluble proteins NSF and SNAP. This so called fusion complex can then disassemble after ATP hydrolysis mediated by the ATPase NSF in a process that leads to membrane fusion and the release of the vesicle contents. t-SNAREs consist of two different families of proteins: the type II integral membrane proteins syntaxins and SNAP-25 (synaptosome-associated protein of 25 kDa), which is anchored in the plasma membrane by attached lipids and does not span the membrane [1].

The N- and C-terminal coiled-coil domains of members of the SNAP-25 family and the most C-terminal coiled-coil domain of the syntaxin family are related to each other and form a new homology domain of approximately 60 amino acids. This domain is also found in other known proteins involved in vesicular membrane traffic, some of which belong to different protein families [1]:

• Yeast SFT1, UFE1, BET1, VAM7 and YDR468c proteins.
• Mammalian TSL-4 proteins.

The profile we developed covers the entire t-SNARE coiled-coil homology domain.