金环蛇毒膜活性多肽B在脂双层中形成离子通道的作用

利用由卵磷脂和胆固醇(分别为20和5mg/ml)的正癸烷溶液形成的平板脂双层,观察了由金环蛇毒纯化的膜活性多肽B(BMAP B)形成通道的作用。实验结果表明,在膜两侧有一定电位差或盐浓度梯度的条件下,BMAP B参入脂双层形成离子通道,在电压箝位下可记录出不同电导的单位电导涨落,随着更多通道的形成,脂双层稳态膜电阻明显降低;通过在不对称盐溶液中测定平衡电位,确定BMAP B通道的阴阳离子选择性不强,P_K/P_Cl≈1.4;和在生物膜的作用一样,二价金属离子Ba~(2+),Ca~(2+)抑制BMAP B通道的活动。这些结果为金环蛇毒膜活性多肽在生物膜的去极化作用提供了解释。

CHANNEL-FORMING ACTIVITY AT PLANAR LIPID BILAYER OF THE MEMBRANE ACTIVE POLYPTIDE B FORM VENOM OF BUNGARUS FASCIATUS

Using planar lipid bilayer formed by lecithin and cholesterol (20 and 5 mg/mlrespectively in N-decane) the channel-forming activity of the membrane activepolypeptidc B(BMAP B) from the venom of Bungarus fasciatus was investigated.Under the existance of a voltage or a salt concentration gradient between two sidesof the bilayer, unit conductance fluctuation and a decrease in steady state resistanceaccompanying BMAP B incorporation and channel formation were observed. Bymeasuring the reversal potential in an asymmetric solution, the selectiviy of theBMAP B-channel was estimated having a value of P_K/P_(Cl)=1.4. Divalent cations,such as Ba~(2+), Ca~(2+) inhibited the channel activity as they did in biomembranes.These data might provide an explanation for the depolarizing effect of the mem-brane active polypeptide on the native membranes.