Indrasith L S, Izuhara M, Kobayashi M, Yamashita O
Laboratory of Sericultural Science, Faculty of Agriculture, Nagoya University, Japan.
Arch Biochem Biophys. 1988 Nov 15;267(1):328-33. doi: 10.1016/0003-9861(88)90038-0.
A yolk protein, egg-specific protein (ESP), of Bombyx mori is sequentially degraded by the ESP-specific protease which appears at the later stages of embryogenesis. In order to find the biological origin of this protease, an in vitro translation was done on RNAs prepared throughout embryogenesis using a rabbit reticulocyte lysate. Among several peptides translated, a 26-kDa peptide was selectively precipitated by the ESP protease antiserum. The mRNA activity increased slowly and then abruptly, reaching the maximum level on Day 8 of embryogenesis. By cotranslation with dog pancreatic microsomal membranes, the 26-kDa peptide was converted to a 24.5-kDa peptide, suggesting the cleavage of a signal peptide of 1.5 kDa. The direct incubation of the translation mixture with ESP failed to hydrolyze ESP, whereas the immunoprecipitate of the primary translation products clearly hydrolyzed ESP into the same peptides as were given by the authentic ESP protease. These results indicate that the protease becomes biologically active before chemical maturation.
家蚕的一种卵黄蛋白，即卵特异性蛋白（ESP），在胚胎发育后期会被ESP特异性蛋白酶依次降解。为了找到这种蛋白酶的生物学来源，使用兔网织红细胞裂解物对整个胚胎发育过程中制备的RNA进行了体外翻译。在翻译出的几种肽中，一种26 kDa的肽被ESP蛋白酶抗血清选择性沉淀。mRNA活性先缓慢增加，然后突然升高，在胚胎发育第8天达到最高水平。通过与犬胰腺微粒体膜共翻译，26 kDa的肽转化为24.5 kDa的肽，这表明有一个1.5 kDa的信号肽被切割。将翻译混合物与ESP直接孵育未能水解ESP，而初级翻译产物的免疫沉淀物则能将ESP清楚地水解成与正宗ESP蛋白酶产生的相同肽段。这些结果表明，该蛋白酶在化学成熟之前就已具有生物活性。
