Molecular Evolution of Growth Hormone and Classification of Fishes

本项目的目标是在序列比较的基础上构建生长激素和催乳素家族的分子系统发育树，并利用氨基酸变化比例半量化动物的系统发育距离。尽管大量的生长激素和催乳素的结构信息现在是可用的，它仍然局限于哺乳动物和硬骨动物物种。我们从系统发育的关键物种中分离出生长激素和催乳素，并确定了以下物种的完整氨基酸序列：从爬行动物（鳄鱼和海龟），两栖动物（牛蛙）中提取生长激素。原始硬骨鱼（鲟鱼）、硬骨鱼（大西洋鳕鱼、鲶鱼、比目鱼）、蓝鲨；哺乳动物（鲸鱼和抹香鲸）、爬行动物（短吻鳄、鳄鱼、海龟）、两栖动物（牛蛙）、原始硬骨鱼（肺鱼）、硬骨鱼（鲶鱼和比目鱼）的催乳素。在这次调查过程中，我们发现了一种新的水果……从硬骨鱼物种，如大西洋鳕鱼、比目鱼和鲑鱼中发现了更多的蛋白质。完整的氨基酸序列分析表明，该蛋白与生长激素和催乳素有亲缘关系。因此，作为生长激素催乳素家族的新成员，这种蛋白质被命名为“somatolactin”。采用Fitch和Margoliash的方法构建了生长激素的分子系统发育树，包括四足动物和硬骨鱼。硬骨鱼的躯干比四足动物的躯干大得多，这表明四足动物在分子进化过程中更大程度上保留了生长激素。突变变化的程度与系统发育很好地吻合。因此，这些物种的系统发育距离可以通过每100个残基的氨基酸变化来半量化。通过序列比较，估计了生长激素、催乳素和生长肌动素的进化关系。这一估计表明，这些垂体激素通过基因复制从一个共同的祖先分化而来。少

The goal of the project is to construct a molecular phylogenetic tree of the growth hormone and prolactin family on the basis of sequence comparisons and to semi-quantify the phylogenetic distance of animals using ratios of amino acid changes. Although a substantial amount of structural information is now available on growth hormones and prolactins, it is still limited to mammalian and teleostean species. We have isolated growth hormones and prolactins from the species which are key-species in phylogeny and determined the complete amino acid sequences of the followings ; growth hormones from reptiles (crocodile and sea turtle), amphibian (bullfrog). Primitive bony fish (sturgeon), teleosts (Atlantic cod, catfish, flounder), elasmobranch (blue shark) ; prolactin from mammals (sei and sperm whale), reptiles (alligator, crocodile, sea turtle), amphibian (bullfrog), primitive bony fish (lungfish), teleosts (catfish and flounder). In the course of this investigation, we found a novel pituit … More ary protein from teleost species, such as Atlantic cod, flounder, and chum salmon. Elucidation of the complete amino acid sequences revealed that the proteins are distantly and similarly related to grow hormone and prolactin. Consequently, the protein, which is a new member of the growth hormone prolactin family, was named "somatolactin". A molecular phylogenetic tree of growth hormones which was constructed by the method of Fitch and Margoliash consists of two trunks, tetrapods and teleosts. The teleost trunk is much bigger than the tetrapod trunk, indicating the greater conservation of tetrapod growth hormones during molecular evolution. The degree of mutational changes is in good conformity with phylogeny. Therefore, phylogenetic distances of these species could be semi-quantified by amino acid changes per 100 residues. Evolutionary relationship of growth hormone, prolactin and somatolactin was also estimated by sequence comparison. The estimation suggests that these pituitary hormones diverged from a common ancestor by gene duplication. Less