Tilney L G, Hatano S, Ishikawa H, Mooseker M S
J Cell Biol. 1973 Oct;59(1):109-26. doi: 10.1083/jcb.59.1.109.
When Asterias or Thyone sperm come in contact with egg jelly, a long process which in Thyone measures up to 90 microm in length is formed from the acrosomal region. This process can be generated in less than 30 s. Within this process is a bundle of microfilaments. Water extracts prepared from acetone powders of Asterias sperm contain a protein which binds rabbit skeletal muscle myosin forming a complex whose viscosity is reduced by ATP. Within this extract is a protein with the same molecular weight as muscle actin. It can be purified either by collecting the pellet produced after the addition of Mg(++) or by reextracting an acetone powder of actomyosin prepared by the addition of highly purified muscle myosin to the extract. The sperm actin can be polymerized and by electron microscopy the polymer is indistinguishable from muscle F-actin. The sperm actin was shown to be localized in the microfilaments in the acrosomal processes by: (a) heavy meromyosin binding in situ, (b) sodium dodecyl sulfate (SDS) gel electrophoresis of the isolated acrosomal processes and a comparison to gels of flagella which contain no band corresponding to the molecular weight of actin, and (c) SDS gel electrophoresis of the extract from isolated acrosomal caps. Since the precursor for the microfilaments in the unreacted sperm appears amorphous, we suspected that the force for the generation of the acrosomal process is brought about by the polymerization of the sperm actin. This supposition was confirmed, for when unreacted sperm were lysed with the detergent Triton X-100 and the state of the actin in the sperm extract was analyzed by centrifugation, we determined that at least 80% of the actin in the unreacted sperm was in the monomeric state.
当海盘车或海仙人掌的精子与卵胶膜接触时，在海仙人掌中，一个长达90微米的长突起会从顶体区域形成。这个过程能在不到30秒内产生。在这个突起中有一束微丝。从海盘车精子的丙酮粉末制备的水提取物中含有一种蛋白质，它能与兔骨骼肌肌球蛋白结合形成一种复合物，其粘度会被ATP降低。在这种提取物中有一种与肌肉肌动蛋白分子量相同的蛋白质。它可以通过收集添加Mg(++)后产生的沉淀来纯化，或者通过重新提取向提取物中添加高度纯化的肌肉肌球蛋白后制备的肌动球蛋白丙酮粉末来纯化。精子肌动蛋白可以聚合，通过电子显微镜观察，这种聚合物与肌肉F - 肌动蛋白无法区分。精子肌动蛋白通过以下方式被证明定位于顶体突起的微丝中：(a)原位重酶解肌球蛋白结合，(b)对分离出的顶体突起进行十二烷基硫酸钠(SDS)凝胶电泳，并与不含对应肌动蛋白分子量条带的鞭毛凝胶进行比较，以及(c)对分离出的顶体帽提取物进行SDS凝胶电泳。由于未反应精子中微丝的前体看起来无定形，我们怀疑顶体突起产生的力是由精子肌动蛋白的聚合引起的。这一假设得到了证实，因为当用去污剂Triton X - 100裂解未反应的精子，并通过离心分析精子提取物中肌动蛋白的状态时我们确定，未反应精子中至少80%的肌动蛋白处于单体状态。
