Gerton G L
Adv Exp Med Biol. 1986;207:133-49. doi: 10.1007/978-1-4613-2255-9_9.
The envelopes that enclose the eggs of the amphibian Xenopus laevis were isolated and examined for biochemical correlates of the ultrastructural and sperm penetrability differences among the coelomic egg envelope (CE), the vitelline envelope (VE), and the fertilization envelope (FE). By sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the 43,000 molecular weight glycoproteins of CEs were found to be converted to components with molecular weights of 41,000 in VEs; also, a protein with a molecular weight of 57,000 was added to the envelope during the CE-to-VE conversion. The molecular weights of two components decreased during the VE-to-FE conversion, from 69,000 and 64,000 in the VE to 66,000 and 61,000 in the FE. Components from the cortical granules and the innermost jelly coat were also added to the newly-formed FE. As detected by iodination with lactoperoxidase or IODOGEN, both the CE-to-VE and the VE-to-FE conversions caused conformational changes in envelope glycoproteins. Peptide mapping demonstrated that the 43,000 molecular weight components of CE were precursors to the 41,000 molecular weight components of VE and the 69,000 and 64,000 molecular weight components of VE were precursors to the 66,000 and 61,000 molecular weight components of FE. The CE-to-VE conversion presumably occurs in the first portion of the oviduct. Experiments probing the VE-to-FE conversion demonstrated the need for an intact jelly coat for the molecular weight changes to occur. Sperm were not required for the envelope alteration; the SDS-PAGE pattern of envelopes from jellied eggs activated with the Ca++-ionophore A23187 were indistinguishable from the FE. These studies show that there are molecular correlates of the morphological and biological differences among the envelopes. The CE-to-VE and the VE-to-FE conversions follow a similar pattern: in both cases, material is added to the envelope and there are changes in the molecular weights of some of the components.
对非洲爪蟾（Xenopus laevis）卵的包膜进行分离，并检测其超微结构以及卵周膜（CE）、卵黄膜（VE）和受精膜（FE）之间精子穿透性差异的生化相关性。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）发现，卵周膜中分子量为43,000的糖蛋白在卵黄膜中转变为分子量为41,000的成分；此外，在从卵周膜向卵黄膜转变过程中，一种分子量为57,000的蛋白质添加到了包膜中。在从卵黄膜向受精膜转变过程中，两种成分的分子量降低，从卵黄膜中的69,000和64,000降至受精膜中的66,000和61,000。来自皮质颗粒和最内层胶膜的成分也添加到了新形成的受精膜中。通过用乳过氧化物酶或碘代甘脲进行碘化检测发现，从卵周膜到卵黄膜以及从卵黄膜到受精膜的转变都会导致包膜糖蛋白发生构象变化。肽图谱分析表明，卵周膜中分子量为43,000的成分是卵黄膜中分子量为41,000成分的前体，而卵黄膜中分子量为69,000和64,000的成分是受精膜中分子量为66,000和61,000成分的前体。从卵周膜到卵黄膜的转变可能发生在输卵管的第一部分。对从卵黄膜到受精膜转变的实验探究表明，需要完整的胶膜才能发生分子量变化。包膜改变不需要精子；用钙离子载体A23187激活的带胶膜卵的包膜的SDS-PAGE图谱与受精膜无法区分。这些研究表明，包膜之间的形态学和生物学差异存在分子相关性。从卵周膜到卵黄膜以及从卵黄膜到受精膜的转变遵循相似模式：在这两种情况下，都有物质添加到包膜中，并且一些成分的分子量会发生变化。
