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的胰岛素相关多肽--家蚕素进行了基因分析。1)利用抗PTTH合成片段的单抗，从家蚕脑表达文库中克隆了一个编码PTTH的基因。从该基因的编码区推导出106个氨基酸的序列。结果表明，PTTH是由两个106个氨基酸通过二硫键连接而成的同源二聚体。2)利用与家蚕毒素A-链和B-链相对应的人工合成的寡核苷酸，克隆了家蚕毒素的cDNA和基因。家蚕素是首次合成的前体蛋白，其结构为信号肽/B链/C肽/A链。这种结构域组织与前胰岛素一样。家蚕基因组中存在多个家蚕毒素基因拷贝。已经确定了27个拷贝的特征。它们以这样一种特有的方式组织起来，即两个基因形成一对，每对基因中的基因以不同的方式转录。3)从另一只蓖麻蛾中分离出六个类似家蚕毒素的基因。它们在基因组中的结构和组织结构与家蚕毒素基因非常相似。4)原位杂交表明，家蚕毒素基因在家蚕脑的四对中背部神经分泌细胞中空间表达。

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.