Actin in triton-treated cortical preparations of unfertilized and fertilized sea urchin eggs
Actin in triton-treated cortical preparations of unfertilized and fertilized sea urchin eggs
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经 Triton 处理的未受精和受精海胆卵皮质制剂中的肌动蛋白
作者：
A. Spudich;J. Spudich
在大于或等于5 mM EGTA存在下制备的未受精和受精海胆卵的Triton处理的皮质片段含有总卵肌动蛋白的15-30%。然而，肌动蛋白丝是不容易明显的电子显微镜下的皮质碎片未受精卵，但许多受精卵。大部分与未受精卵的皮质片段相关的肌动蛋白通过对pH 7.5的低离子强度缓冲液透析而溶解。这种可溶性肌动蛋白制剂（纯度低于50%的肌动蛋白）在0.1 M KCl和3 mM MgCl 2中不能形成适当的细丝，而从这种制剂中纯化的肌动蛋白则可以，这是通过电子显微镜判断的。光学衍射分析表明，这些纯化的肌动蛋白丝的螺旋参数非常相似的肌肉肌动蛋白。此外，纯化的肌动蛋白激活肌球蛋白ATP酶的特性与其他细胞类型的肌动蛋白相似。肌动蛋白是保持在一个非丝状的形式在未受精卵质膜的内表面上，并诱导受精后组装的可能性进行了讨论。
Triton-treated cortical fragments of unfertilized and fertilized sea urchin eggs prepared in the presence of greater than or equal to 5 mM EGTA contain 15-30% of the total egg actin. However, actin filaments are not readily apparent by electron microscopy on the cortical fragments of unfertilized eggs but are numerous on those of fertilized eggs. The majority of the actin associated with cortical fragments of unfertilized eggs is solubilized by dialysis against a low ionic strength buffer at pH 7.5. This soluble actin preparation (less than 50% pure actin) does not form proper filaments in 0.1 M KCl and 3 mM MgCl2, whereas actin purified from this preparation does, as judged by electron microscopy. Optical diffraction analysis reveals that these purified actin filaments have helical parameters very similar to those of muscle actin. Furthermore, the properties of the purified actin with regard to activation of myosin ATPase are similar to those of actin from other cell types. The possibility that actin is maintained in a nonfilamentous form on the inner surface of the unfertilized egg plasma membrane and is induced to assemble upon fertilization is discussed.