SNARE protein (of Qc type) involved in membrane fusion probably in retrograde traffic of cytosolic double-membrane vesicles derived from both, early and possibly late endosomes/PVC (prevacuolar compartment) back to the trans-Golgi network (TGN or late Golgi). It has been reported to function both as a (target membrane) t-SNARE and as a (vesicle) v-SNARE. Upon vesicle tethering to the target membrane, which requires additional proteins, a SNARE-pin is formed. This is a very stable 4 parallel alpha-helical coil bundle consisting of 4 SNARE domains (usually one of each type: Qa, Qb, Qc, and R), of which at least one is anchored in the opposite membrane. The formation of the SNARE-pin is believed to bring the two membranes in close proximity and to provide the energy to drive membrane fusion. Through its interaction with the VFT (or GARP) complex, it may also contribute to vesicle recognition specificity and tethering. Regulation of SNARE-pin formation also seems to depend on the phosphorylation state of the protein, phosphorylation by TPK1 causing inhibition and dephosphorylation by SIT4 activation. Interacts in a SNARE-pin with the SNAREs TLG2 (Qa), VTI1 (Qb), and SNC1 or SNC2 (R). Interacts with VPS51 of the VFT (or GARP) complex. Probably shuttling between TGN and early/late endosome. Phosphorylated at Thr-31 by TPK1 and dephosphorylated by SIT4. Palmitoylated by SWF1, which prevents its recognition and ubiquitination by TUL1 and its subsequent degradation. Belongs to the syntaxin family.