Insertion of a neomycin resistance cassette into intron 1 and an arginine to glutamine point mutation at position 233 of exon 1 (R233Q) was introduced via homologous recombination. Western blot of brain homogenates from homozygous mutant animals verified the presence of protein expression and enzyme assays demonstrated similar phospholipid- and syntaxin-binding ability compared to wild-type. However, calcium affinity was decreased by 2-fold. (J:76452)