Mabuchi I, Hamaguchi Y, Kobayashi T, Hosoya H, Tsukita S, Tsukita S
J Cell Biol. 1985 Feb;100(2):375-83. doi: 10.1083/jcb.100.2.375.
A protein similar to alpha-actinin has been isolated from unfertilized sea urchin eggs. This protein co-precipitated with actin from an egg extract as actin bundles. Its apparent molecular weight was estimated to be approximately 95,000 on an SDS gel: it co-migrated with skeletal-muscle alpha-actinin. This protein also co-eluted with skeletal muscle alpha-actinin from a gel filtration column giving a Stokes radius of 7.7 nm, and its amino acid composition was very similar to that of alpha-actinins. It reacted weakly but significantly with antibodies against chicken skeletal muscle alpha-actinin. We designated this protein as sea urchin egg alpha-actinin. The appearance of sea urchin egg alpha-actinin as revealed by electron microscopy using the low-angle rotary shadowing technique was also similar to that of skeletal muscle alpha-actinin. This protein was able to cross-link actin filaments side by side to form large bundles. The action of sea urchin egg alpha-actinin on the actin filaments was studied by viscometry at a low-shear rate. It gelled the F-actin solution at a molar ratio to actin of more than 1:20, at pH 6-7.5, and at Ca ion concentration less than 1 microM. The effect was abolished by the presence of tropomyosin. Distribution of this protein in the egg during fertilization and cleavage was investigated by means of microinjection of the rhodamine-labeled protein in the living eggs. This protein showed a uniform distribution in the cytoplasm in the unfertilized eggs. Upon fertilization, however, it was concentrated in the cell cortex, including the fertilization cone. At cleavage, it seemed to be concentrated in the cleavage furrow region.
一种类似于α-辅肌动蛋白的蛋白质已从未受精的海胆卵中分离出来。这种蛋白质与卵提取物中的肌动蛋白一起以肌动蛋白束的形式共沉淀。在SDS凝胶上，其表观分子量估计约为95,000：它与骨骼肌α-辅肌动蛋白迁移率相同。这种蛋白质也与骨骼肌α-辅肌动蛋白从凝胶过滤柱上共同洗脱，斯托克斯半径为7.7纳米，其氨基酸组成与α-辅肌动蛋白非常相似。它与抗鸡骨骼肌α-辅肌动蛋白的抗体反应较弱但明显。我们将这种蛋白质命名为海胆卵α-辅肌动蛋白。使用低角度旋转阴影技术通过电子显微镜观察到的海胆卵α-辅肌动蛋白的外观也与骨骼肌α-辅肌动蛋白相似。这种蛋白质能够使肌动蛋白丝并排交联形成大束。通过低剪切速率下的粘度测定研究了海胆卵α-辅肌动蛋白对肌动蛋白丝的作用。在pH 6 - 7.5、钙离子浓度小于1微摩尔时，它以与肌动蛋白摩尔比大于1:20使F-肌动蛋白溶液凝胶化。原肌球蛋白的存在消除了这种作用。通过将罗丹明标记的蛋白质显微注射到活卵中来研究这种蛋白质在受精和卵裂过程中在卵内的分布。这种蛋白质在未受精卵的细胞质中呈均匀分布。然而，受精后，它集中在细胞皮层，包括受精锥。在卵裂时，它似乎集中在卵裂沟区域。
