A Ca2+-activated channel from Xenopus laevis oocyte membranes reconstituted into planar bilayers.
A Ca2+-activated channel from Xenopus laevis oocyte membranes reconstituted into planar bilayers.
复制标题
来自非洲爪蟾卵母细胞膜的 Ca2 激活通道重构为平面双层。
DOI：
10.1073/pnas.81.16.5155
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发表时间：
1984
影响因子：
11.1
通讯作者：
Cohn,ZA
中科院分区：
文献类型：
--
作者：
Young,GP;Young,JD;Deshpande,AK;Goldstein,M;Koide,SS;Cohn,ZA
将非洲爪蟾卵母细胞的质膜部分掺入平面脂质双层中。我们证明存在许多 Ca2+ 激活的非特异性通道，这些通道对阴离子更具渗透性。这些通道可被微摩尔浓度的 Ca2+ 激活，但不会被 Mg2+、Zn2+ 或 Mn2+ 激活，即使在毫摩尔浓度下也是如此。将 Ca2+ 浓度降低至 1 µM 以下会缩短通道开放时间，直至通道在不存在 Ca2+ 且存在 EGTA 的情况下完全关闭。 I- 和 Br- 比 Cl- 更容易通过该通道。通道保持打开的时间也与电压有关，通道在两种极性的较高电压下都会关闭。单通道活性在 1 M NaCl 和 1 mM CaCl2 中显示出 380 pS 的电导，在 40 mV 下的平均开放寿命为 1.5 s。在卵母细胞成熟的不同阶段也发现了类似的通道。这些观察结果支持这样的假设：不含卵母细胞的 Ca2+ 的增加直接激活这些通道，并且由此产生的 Cl- 流出形成了 X. laevis 受精潜力的离子基础。
Plasma membrane fractions from Xenopus laevis oocytes were incorporated into planar lipid bilayers. We show the existence of numerous Ca2+-activated nonspecific channels that are more permeable to anions. These channels are activated by Ca2+ at micromolar concentration but not by Mg2+, Zn2+, or Mn2+, even at millimolar concentrations. Decreasing Ca2+ concentration to less than 1 microM decreases the time of channel opening until channels close completely in the absence of Ca2+ and in the presence of EGTA. I- and Br- are more permeable through this channel than Cl-. The time during which the channels remain open is also voltage-dependent, with the channels switching off at higher voltages in both polarities. Single-channel activity shows a conductance of 380 pS in 1 M NaCl and 1 mM CaCl2, with an average open lifetime of 1.5 s at 40 mV. Similar channels are found in different stages of oocyte maturation. These observations support the hypothesis that an increase in oocyte-free Ca2+ activates directly these channels, and the resultant Cl- efflux forms the ionic basis for the fertilization potential in X. laevis.