Wittenberg C, Kohl D M, Triplett E L
Cell Differ. 1978 Apr;7(1-2):11-20. doi: 10.1016/0045-6039(78)90003-9.
In previous publications we have documented the existence in oocytes and embryos of a variety of forms (notably Rana pipiens), massive amounts of a powerful inhibitor of trypsin-like enzymes (ATI). The bulk of the inhibitor in Rana pipiens is localized in yolk platelets. We present evidence here that the distribution of the inhibitor between yolk platelets and cytosol changes and that this change is mediated by variations in the distribution of calcium ions. There is an inverse relationship between ATI and free calcium in the cytosol. Several workers have demonstrated a dramatic rise in free cytosol calcium immediately following fertilization. We confirm this observation, and demonstrate that there is a parallel and equally dramatic decrease in free cytosol ATI during this period. Experiments with purified yolk platelets indicate that calcium effects a release of sequestered inhibitor from these particles. Other experiments indicate that calcium mediates ATI-lippovitellin associations. A calcium mediated flux of ATI from cytosol to yolk is proposed as a device for controlling limited proteolysis in the cytoplasm. We offer this as a model for studying the unmasking of mRNA which follows fertilization.
在之前的出版物中，我们记录了在卵母细胞和胚胎中存在多种形式（特别是豹蛙）的大量强力胰蛋白酶样酶抑制剂（ATI）。豹蛙中的大部分抑制剂定位于卵黄小板中。我们在此提供证据表明，抑制剂在卵黄小板和细胞质溶胶之间的分布发生了变化，并且这种变化是由钙离子分布的变化介导的。细胞质溶胶中的ATI与游离钙之间存在反比关系。几位研究人员已经证明，受精后细胞质溶胶中的游离钙会立即急剧上升。我们证实了这一观察结果，并表明在此期间细胞质溶胶中的游离ATI也会平行且同样急剧下降。对纯化的卵黄小板进行的实验表明，钙会导致这些颗粒中螯合的抑制剂释放出来。其他实验表明，钙介导了ATI与脂蛋白的结合。我们提出，钙介导的ATI从细胞质溶胶到卵黄的通量是一种控制细胞质中有限蛋白水解的机制。我们将此作为研究受精后mRNA解蔽的模型。
