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Potent, specific L-type Ca2+ channel blocker (IC50 = 15 nM). Inactive on other voltage-dependent Ca2+ channels. Smooth muscle relaxant and cardia contraction inhibitor. Neurotoxic. Active in vivo and in vitro.
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
History
The black mamba (Dendroaspis polylepis) is generally considered to be one of the deadliest snakes on the planet,and is responsible for many fatalities throughout its sub-Saharan Africa range. Without treatment, the bite of a Black Mamba causes a 100% mortality rate.
The venom of the Black Mamba consists of more than 28 peptides. One of these peptides is calciseptine. It makes up 2.8% of the venom of the Black Mamba. When first purified, the peptide was called protein E3, which was later changed to calciseptine by Weille et al.
Sequence and structure
Calciseptine itself consists of 60 amino acids and has been fully sequenced:
RICYIHKASL PRATKTCVEN TCYKMFIRTQ REYISERGCG CPTAMWPYQT ECCKGDRCNK
The three-dimensional structure of calciseptine has not been determined experimentally. However, another toxin found in black mamba venom, called FS2, sequentially differs from calciseptine in only three residues: it contains a serine instead of isoleucine in position 5, a histidine instead of glutamine in position 30, and a glutamine instead of glutamic acid in position 32. A three-dimensional structure of FS2 has been determined using NMR, and because of the minor sequential differences, this can serve as a model of the calciseptine structure
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Potent, specific L-type Ca2+ channel blocker (IC50 = 15 nM). Inactive on other voltage-dependent Ca2+ channels. Smooth muscle relaxant and cardia contraction inhibitor. Neurotoxic. Active in vivo and in vitro.
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
History
The black mamba (Dendroaspis polylepis) is generally considered to be one of the deadliest snakes on the planet,and is responsible for many fatalities throughout its sub-Saharan Africa range. Without treatment, the bite of a Black Mamba causes a 100% mortality rate.
The venom of the Black Mamba consists of more than 28 peptides. One of these peptides is calciseptine. It makes up 2.8% of the venom of the Black Mamba. When first purified, the peptide was called protein E3, which was later changed to calciseptine by Weille et al.
Sequence and structure
Calciseptine itself consists of 60 amino acids and has been fully sequenced:
RICYIHKASL PRATKTCVEN TCYKMFIRTQ REYISERGCG CPTAMWPYQT ECCKGDRCNK
The three-dimensional structure of calciseptine has not been determined experimentally. However, another toxin found in black mamba venom, called FS2, sequentially differs from calciseptine in only three residues: it contains a serine instead of isoleucine in position 5, a histidine instead of glutamine in position 30, and a glutamine instead of glutamic acid in position 32. A three-dimensional structure of FS2 has been determined using NMR, and because of the minor sequential differences, this can serve as a model of the calciseptine structure