PURIFICATION, SEQUENCE, AND MODEL STRUCTURE OF CHARYBDOTOXIN, A POTENT SELECTIVE INHIBITOR OF CALCIUM-ACTIVATED POTASSIUM CHANNELS
PURIFICATION, SEQUENCE, AND MODEL STRUCTURE OF CHARYBDOTOXIN, A POTENT SELECTIVE INHIBITOR OF CALCIUM-ACTIVATED POTASSIUM CHANNELS
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DOI：
10.1073/pnas.85.10.3329
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发表时间：
1988-05-01
影响因子：
11.1
通讯作者：
GARCIA, ML
中科院分区：
文献类型：
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作者：
GIMENEZGALLEGO, G;NAVIA, MA;GARCIA, ML
Charybdotoxin（ChTX）是一种存在于五纹蝎Leiurus quinquestriatus var. Hebraeus，已经通过离子交换和反相色谱法的组合纯化至均一。聚丙烯酰胺凝胶电泳，氨基酸分析，和完整的氨基酸序列测定的纯蛋白质表明，它由一个单一的多肽链的4.3 kDa。纯化的ChTX是存在于GH 3垂体前叶细胞和原代牛主动脉平滑肌细胞中的ap 220-pS Ca 2+激活的K+通道的有效和选择性抑制剂。该毒素通过与通道蛋白的外孔相互作用可逆地阻断通道活性，表观Kd为2.1 nM。ChTX的一级结构类似于许多不同来源的神经毒素，这表明ChTX是改变离子通道活性的超家族或蛋白质的成员。基于这种相似性，ChTX的三维结构已经由α-ChTX的已知晶体结构建模。银环蛇毒素这些研究表明，ChTX是有用的作为探针的Ca 2+激活的K+通道功能，并建议，建议的ChTX的三级结构可以提供深入了解通道阻滞的机制。
Charybdotoxin (ChTX), a protein present in the venom of the scorpion Leiurus quinquestriatus var. hebraeus, has been purified to homogeneity by a combination of ion-exchange and reversed-phase chromotography. Polyacrylamide gel electrophoresis, amino acid analysis, and complete amino acid sequence determination of the pure protein reveal that it consists of a single polypeptide chain of 4.3 kDa. Purified ChTX is a potent and selective inhibitor of the .apprxeq.220-pS Ca2+-activated K+ channel present in GH3 anterior pituitary cells and primary bovine aortic smooth muscle cells. The toxin reversibly blocks channel activity by interacting at the external pore of the channel protein with an apparent Kd of 2.1 nM. The primary structure of ChTX is similar to a number of neurotoxins of diverse origin, which suggests that ChTX is a member of a superfamily or proteins that modify ion-channel activities. On the basis of this similarity, the three-dimensional structure of ChTX has been modeled from the known crystal structure of .alpha.-bungarotoxin. These studies indicate that ChTX is useful as a probe of Ca2+-activated K+-channel function and suggest that the proposed tertiary structure of ChTX may provide insight into the mechanism of channel block.