Title: Calciseptine
CAS Registry Number: 134710-25-1
Literature References: Peptide toxin, 60 amino acids long with 4 disulfide bridges, isolated from the venom of the black mamba snake (Dendroaspis polylepis polylepis); specific blocker of L-type Ca2+ channels. Isoln and characterization: J. R. De Weille et al., Proc. Natl. Acad. Sci. USA 88, 2437 (1991). Solution synthesis: H. Kuroda et al., Peptide Res. 5, 265 (1992). NMR 3d structure determn: H. Haruyama et al., Bull. Magn. Reson. 18, 125 (1996). Analysis of residues involved in binding: R. M. Kini et al., Biochemistry 37, 9058 (1998). Differential sensitivities to L-channel subtypes: C. M. Rogers, E. R. Brown, Exp. Physiol. 86, 689 (2001). Comparison with 1,4-dihydropyridines of effects on smooth muscle: T. X. Watanbe et al., Jpn. J. Pharmacol. 68, 305 (1995); on skeletal muscle: M. C. Garcia et al., J. Membr. Biol. 184, 121 (2001).
Use: Biochemical probe for L-type Ca2+ channels.
Calcitonin Calcium 2-Ethylbutanoate Calcium 3-Aurothio-2-propanol-1-sulfonate Calcium Acetate Calcium Acetylsalicylate

Formula C299H476N90O87S10
Molecular weight 7036 g/mol
3D model of calciseptine structure
A model of the 3D structure of calciseptine, based on an NMR structure of its homologue FS2. Disulfide bridges are shown in yellow. The three residues that differ between FS2 and calciseptine are shown in red.

Calciseptine (CaS) is a natural neurotoxin isolated from the black mamba Dendroaspis p. polylepis venom. This toxin consists of 60 amino acids with four disulfide bonds. Calciseptine specifically blocks L-type calcium channels, but not other voltage-dependent Ca2+ channels such as N-type and T-type channels.[1]