Johnson K S, Taylor D W, Cordingley J S
Mol Biochem Parasitol. 1987 Jan 2;22(1):89-100. doi: 10.1016/0166-6851(87)90072-7.
We have identified and sequenced a cDNA clone of a mRNA found only in mature female schistosomes. This mRNA is not detectably synthesized by female worms from single sex infections (unisexual females), by males or by the developing miracidia in the eggs. The clone hybridises to a highly abundant polyadenylated mRNA of approximately 1500 nucleotides. The nucleotide sequence of the clone predicts a polypeptide comprising two repetitive regions. A pentapeptide repeat with the consensus sequence Gly-Tyr-Asp-Lys-Tyr, and a region rich in histidine residues. Hybrid selected mRNA translated in vitro with [3H]tyrosine as labelled amino acid yields a polypeptide of 48 kDa (p48) that corresponds to the major [3H]tyrosine labelled translation product of female worm total mRNA. p48 does not label with [35S]methionine and is absent from the translation products of male and unisexual female mRNAs. The amino acid sequence of p48 has significant homologies to silk moth chorion proteins and we suggest that it is one of the major components of the schistosome eggshell probably accounting for the high level of [3H]tyrosine incorporation into the vitellaria of Schistosoma mansoni. The tyrosine content of the polypeptide suggests that it may play a role in phenol oxidase mediated cross-linking of the schistosome eggshell and in support of this we find that mushroom phenol oxidase will cause the specific cross-linking of p48 in in vitro translation products.
我们已经鉴定并测序了一种仅在成熟雌性血吸虫中发现的mRNA的cDNA克隆。这种mRNA在单性感染的雌虫（孤雌生殖雌虫）、雄虫或卵中的发育毛蚴中均未检测到有明显合成。该克隆与一种约1500个核苷酸的高度丰富的多聚腺苷酸化mRNA杂交。该克隆的核苷酸序列预测了一种包含两个重复区域的多肽。一个具有共有序列Gly-Tyr-Asp-Lys-Tyr的五肽重复序列，以及一个富含组氨酸残基的区域。以[3H]酪氨酸作为标记氨基酸在体外翻译杂交选择的mRNA，产生一种48 kDa的多肽（p48），它对应于雌虫总mRNA的主要[3H]酪氨酸标记翻译产物。p48不能用[35S]甲硫氨酸标记，并且在雄虫和孤雌生殖雌虫mRNA的翻译产物中不存在。p48的氨基酸序列与家蚕卵壳蛋白有显著同源性，我们认为它是血吸虫卵壳的主要成分之一，可能是曼氏血吸虫卵黄腺中[3H]酪氨酸高水平掺入的原因。该多肽的酪氨酸含量表明它可能在酚氧化酶介导的血吸虫卵壳交联中起作用，支持这一观点的是，我们发现蘑菇酚氧化酶会导致体外翻译产物中p48的特异性交联。
