Calciseptine

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.

Sequence
Its amino acid sequence is: RICYI HKASL PRATK TCVEN TCYKM FIRTQ REYIS REGCG CPTAM WPYQT ECCKG DRCNK

Isolation
Calciseptine is purified from the venom of black mamba 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 portal vein, contractions of the rat thoracic aorta, uterus and cardiac preparations.