Gene Analysis for the Prothoracicotropic Hormone of the Silkmoth, Bombyx mori.

对家蚕促前胸腺激素（PTTH）和一种类似PTTH的胰岛素相关肽--从该cDNA的编码区推导出106个氨基酸的序列。结果表明PTTH是由两个106个氨基酸组成的多肽通过二硫键连接而成的同源二聚体。2）利用人工合成的家蚕毒素A链和B链的寡核苷酸序列，克隆了家蚕毒素的cDNA和基因。前体蛋白perprobombyxin首先被合成，其结构为信号肽/B链/C肽/A链。该结构域组织与前胰岛素原相同。多个家蚕毒素基因拷贝存在于家蚕基因组中。27个副本已被定性。3）从蓖麻蚕（Samia cynthia ricini）中分离到6个类似家蚕毒素的基因。4）原位杂交结果显示，家蚕毒素基因在家蚕脑背中部的4对神经分泌细胞中特异性表达。

Gene analyses have been made for the prothoracicotropic hormone(PTTH) and a PTTH-like, insulin-related paptide, Bombyxin, of the silkmoth bombyx mori.1) A cDNA encoding PTTH has been cloned from a cDNA expression library derived from the Bombyx brain using a monoclonal antibody against a synthetic fragment of PTTH. The 106-amino acid sequence was deduced from the coding region of this cDNA. It was concluded that PTTH is a homodimer in which the two 106-amino acid peptides are connected together by disulfide bonds. Two genomic DNA clones encoding PTTH was also cloned.2) Using the synthetic oligonucleotides corresponding to the A- and B-chains of bombyxin, the bombyxin cDNAs and genes have been isolated. Bombyxins are first synthesized as a precursor protein,perprobombyxin, whose structure is signal peptid/B-chain/C-peptide/A-chain. This domain organization is the same as in preproinsulins. Multiple bombyxin gene copies exist in the Bombyx genome. Twentyseven copies have been characterized. They are organized in such a characteristicway that two genes form a pair and the genes in each pair are divergently transcribed.3) Six bombyxin-like genes have been isolated from another moth Samia cynthia ricini. Their structure and organization in the genomo are very similar to those of Bombyx bombyxin genes.4) In situ hybridization showed that bombyxin genes are expressed spacifically in the four pairs of mid-dorsal neurosecretory cells of Bombyx brain.