Binding of sea anemone toxin to receptor sites associated with gating system of sodium channel in synaptic nerve endings in vitro.
Binding of sea anemone toxin to receptor sites associated with gating system of sodium channel in synaptic nerve endings in vitro.
复制标题
海葵毒素与体外突触神经末梢钠通道门控系统相关受体位点的结合。
DOI：
10.1073/pnas.77.3.1646
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发表时间：
1980
影响因子：
11.1
通讯作者：
M. Lazdunski
中科院分区：
文献类型：
--
作者：
J. Vincent;M. Balerna;J. Barhanin;M. Fosset;M. Lazdunski
来自海葵 Anemonia sulcata 的毒素 II 的碘化产生了标记的单碘衍生物，保留了 80% 的原始神经毒性。该衍生物在 20°C、pH 7.4 条件下与大鼠脑突触体特异性结合，二级缔合速率常数 ka = 4.6 x 10(4) M-1 sec-1，一级解离速率常数 kd = 1.1 x 10(-2) sec-1。这种结合发生在 Na+ 通道上，其结合位点与其他门控系统毒素（如蝙蝠毒素、藜芦定、灰木毒素、乌头碱和拟除虫菊酯）的结合位点不同。最大结合能力 Bmax 为 3.2 pmol/mg 蛋白质（即每个河豚毒素结合位点大约有两个海葵毒素结合位点），单碘衍生物的 Kd 为 240 nM，天然毒素的 Kd 为 150 nM。来自蝎子 Androctonus australis Hector 的毒素 II 的 125I 标记衍生物结合的相应结合参数为 Bmax = 0.3 pmol/mg 蛋白质，Kd = 1 nM，而未修饰的蝎子毒素的 Kd 为 0.6 nM。涉及蝎子毒素、海葵毒素和突触体的竞争实验表明，虽然海葵毒素能够取代与突触体结合的蝎子毒素，但蝎子毒素并不能取代海葵毒素。海葵毒素而不是蝎子毒素与去极化的突触体结合。讨论中分析了两种多肽毒素的结合特性之间的差异。
Iodination of toxin II from the sea anemone Anemonia sulcata gives a labeled monoiododerivative that retains 80% of the original neurotoxicity. This derivative binds specifically to rat brain synaptosomes at 20 degrees C and pH 7.4 with a second-order rate constant of association ka = 4.6 x 10(4) M-1 sec-1 and a first-order rate constant of dissociation kd = 1.1 x 10(-2) sec-1. The binding occurs on the Na+ channel at a binding site distinct from that of other gating system toxins like batrachotoxin, veratridine, grayanotoxin, aconitine, and pyrethroids. The maximal binding capacity Bmax is 3.2 pmol/mg of protein (i.e., about two sea anemone toxin binding sites per tetrodotoxin binding site) and the Kd is 240 nM for the monoiododerivative and 150 nM for the native toxin. Corresponding binding parameters for the association of a 125I-labeled derivative of toxin II from the scorpion Androctonus australis Hector are Bmax = 0.3 pmol/mg of protein and Kd = 1 nM, whereas the Kd of the unmodified scorpion toxin is 0.6 nM. Competition experiments involving scorpion toxins, sea anemone toxins, and synaptosomes demonstrate that, although the sea anemone toxin is able to displace the scorpion toxin bound to synaptosomes, the scorpion toxin does not displace the sea anemone toxin. The sea anemone toxin but not the scorpion toxin binds to depolarized synaptosomes. Differences between binding properties of the two polypeptide toxins are analyzed in the discussion.