Technical Data
Synaptotagmin I, p65 (Syt1)
Synaptotagmin (also known as p65) is a synaptic vesicle protein that consists of an amino-terminal intravesicular domain, a single transmembrane domain, and a cytoplasmic domain composed of two repeats homologous to the C2 regulatory domain of protein kinase C. Synaptotagmin forms a homo-oligomer that binds calcium in a complex with negatively charged phospholipids. This observation, along with the fact that no synaptotagmin homolog has yet been identified in the constitutive secretory pathway, suggests that synaptotagmin may function as a calcium sensor that triggers exocytosis. The apparent low affinity for calcium and the multiple binding sites for calcium displayed by synaptotagmin are consistent with the properties expected of the calcium trigger for vesicle fusion. Support for a role of synaptotagmin in synaptic vesicle docking of fusion includes direct interactions with syntaxin and neurexin, and either direct or indirect interactions with N-type calcium channels. The interactions with these three presynaptic plasma membrane proteins could potentially position synaptotagmin, and the vesicle, in an optimal position to respond to calcium. Functional data supportive of a role for synaptotagmin in regulated secretion include the inhibition of secretion generated by microinjection of either synaptotagmin peptides into the squid giant synapse, or soluble synaptotagmin fragments and anti-synaptotagmin antibodies into PC-12 cells. However, genetic studies on PC-12 cells, as well as Drosophila and C. elegans, have demonstrated that synaptotagmin is not absolutely required for regulated neurotransmitter release. This may reflect the ability of another protein, such as rabphillin, to compensate partially for the loss of synaptotagmin. Alternatively, synaptotagmin may not be an essential component of the machinery required for vesicle docking and fusion, but rather may function as a calcium-sensitive negative regulator of the constitutive fusion machinery. This possibility is supported by recent electrophysiological recordings from synaptotagmin-deficient Drosophila, which revealed an increase in spontaneous neurotransmitter release and a decrease in evoked release.

Western Blot (ECL): 1:1,000
Immunoprecipitation: 1:100
Immunocytochemistry: 1:250
Optimal dilutions to be determined by researcher.

Positive Controls:
Rat Brain Tissue Extract
25ul -20CBlue IceRatRabbit
A 23 residue synthetic peptide MVSASHPEALAAPVTTVATLVPH(C) based on the rat synaptotagmin I (residues 1-23) with the cysteine (C) residue added and the peptide coupled to KLH.
Detects a 65kD protein, corresponding to the apparent molecular mass of synaptotagmin I on SDS-PAGE immunoblots, in samples from rat and Xenopus. The antibody specificity is confirmed by peptide inhbition as determined by immunoblot analysis.
Intended for research use only. Not for use in human, therapeutic, or diagnostic applications.
1. Malgaroli, A., Ting, A.E., Wendland, B., Bergamaschi, A., Villa, A., Tsien, R.W., &
Scheller, R.H. (1995) Science 268: 1624-1628