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  • Title: Blocking effect and crystal structure of natrin toxin, a cysteine-rich secretory protein from Naja atra venom that targets the BKCa channel.
    Author: Wang J, Shen B, Guo M, Lou X, Duan Y, Cheng XP, Teng M, Niu L, Liu Q, Huang Q, Hao Q.
    Journal: Biochemistry; 2005 Aug 02; 44(30):10145-52. PubMed ID: 16042391.
    Abstract:
    Cysteine-rich secretory proteins (CRISPs) are widespread in snake venoms. Some members of these CRISPs recently have been found to block L-type Ca(2+) channels or cyclic nucleotide-gated ion (CNG) channels. Here, natrin purified from Naja atra venom, a member of the CRISP family, can induce a further contractile response in the endothelium-denuded thoracic aorta of mouse which has been contracted by a high-K(+) solution. Further experiments show it can block the high-conductance calcium-activated potassium (BK(Ca)) channel in a concentration-dependent manner with an IC(50) of 34.4 nM and a Hill coefficient of 1.02, which suggests that only a single natrin molecule is required to bind an ion channel to block BK(Ca) current. The crystal structure of natrin displaying two domains in tandem shows its cysteine-rich domain (CRD) has relatively independent flexibility, especially for the C-terminal long loop (loop I) of CRD to participate in the interface of two domains. On the basis of previous studies of CNG channel and L-Ca(2+) channel blockers, and the sequence and structural comparison of natrin and stecrisp, the deviation of the vital loop I of CRD is suggested to contribute to different effects of some CRISPs in protein-protein interaction.
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