Synaptotagmin III (SYT3)

Synaptotagmin-1 (SYT1), an integral membrane protein of synaptic vesicles, is thought to be involved in calcium-dependent exocytosis of synaptic vesicles.Synaptotagmin III contains 588 amino acids having 40.5, 38.3, and 64.0% identity with rat synaptotagmin-1, rat synaptotagmin-2 (SYT2), and a third synaptotagmin isoform of the marine ray, respectively. The region of the 2 internal repeats homologous to the regulatory domain of protein kinase C was highly conserved among the 3 synaptotagmins. RNA blot studies demonstrated that synaptotagmin-3 mRNA is expressed in brain, various endocrine tissues, and hormone-secreting clonal cells. It appeared to be involved in Ca(2+)-dependent exocytosis of secretory vesicles in endocrine cells, as well as in neurons.