A targeting vector was designed to place a LoxP-Flp-neomycin-Flp cassette in intron 1, a FLAG-(C)4-FLAG cassette in exon 2, and LoxP site in intron 2. Mutant protein expression levels are similar to those of the wildtype protein. Expression is brain-specific and localized in the neuronal soma and dendrites (presumably on cargo vesicles). Protein can be recognized using FLAG antibody by Western blot analysis, but not in brain sections and labeled cultures. No significant N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) binding is observed in immunoprecipitation (IP) assays.