May be involved in the secretory pathway (By similarity). Essential for membrane fusion mediated by either SYP41 or SYP61; triggers the fusion of phospholipid vesicles containing SYP41 or SYP61 and VTI12 (PubMed:15919093). Interacts with SYP41 (PubMed:15919093). Core constituent of the SNARE complex required for membrane fusion at the trans-Golgi network (PubMed:15919093). A number of isoforms are produced. According to EST sequences. Expressed ubiquitously in roots, stems, flowers and leaves. Belongs to the synaptobrevin family.