| colspan="2" align=center bgcolor="#cccccc" | Calciseptine
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|Molecular weight >

Calciseptine (CaS) is a natural neurotoxin

Neurotoxin

A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...

 isolated from the black mamba Dendroaspis p. polylepis venom

Venom

Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...

. This toxin consists of 60 amino acids with four disulfide bonds. Calciseptine specifically blocks L-Type calcium channel

Calcium channel

A Calcium channel is an ion channel which displays selective permeability to calcium ions. It is sometimes synonymous as voltage-dependent calcium channel, although there are also ligand-gated calcium channels.-Comparison tables:...

s, but not other voltage

Voltage

Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...

-dependent Ca²⁺ channels such as N-type and T-type channels.

Sequence

Its amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

 sequence is: RICYIHKASL PRATKTCVEN TCYKMFIRTQ REYISERGCG CPTAMWPYQT ECCKGDRCNK

Isolation

Calciseptine is purified from the venom of black mamba

Black mamba

The black mamba , also called the common black mamba or black-mouthed mamba, is the longest venomous snake in Africa, averaging around in length, and sometimes growing to lengths of...

 Dendroaspis p. polyepsis via three isolation steps: (1) gel filtration, (2) ion exchange on TSK SP 5PW, and (3) reverse-phase chromatograghy on RP18. It represents 2.8% of the total venom components.

Target

Calciseptine blocks L-type Ca²⁺ channels.
As a result, it blocks spontaneous contractions of rat

Rat

Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

 portal vein, contractions of the rat thoracic aorta

Thoracic aorta

The thoracic aorta is contained in the posterior mediastinal cavity.It begins at the lower border of the fourth thoracic vertebra where it is continuous with the aortic arch, and ends in front of the lower border of the twelfth thoracic vertebra, at the aortic hiatus in the diaphragm where it...

, uterus

Uterus

The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...

and cardiac preparations.