May function in the docking or fusion of transport vesicles with the prevacuolar membrane. Part of the t-SNARE complex (By similarity). Interacts with RGS1. In cv. RLD, probably a type IV membrane protein. In cv. Columbia, probably associated with membranes by a post-translational modification or through protein-protein interactions. A number of isoforms are produced. According to EST sequences. Expressed at higher levels in leaves, flowers and stems than in roots. Addition of one nucleotide in cv. RLD induces a frameshift in position 245 leading to a protein 22 amino acids longer than the one shown here. In cv. RLD, the 22 amino acids extension regenerates a typical syntaxin transmembrane domain. In cv. Columbia it encodes a protein that has no terminal transmembrane domain, but that is however not detected in cytosolic fractions. Belongs to the syntaxin family.