Molecular Evolution of Growth Hormone and Classification of Fishes

该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，并利用氨基酸变化率来半量化动物的系统发育距离。虽然现在已经有大量关于生长激素和催乳素的结构信息，但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，并测定了下列物种的完整氨基酸序列：爬行动物(鳄鱼和海龟)、两栖动物(牛蛙)的生长激素。原始硬骨鱼(鲟鱼)、硬骨鱼(大西洋鳕鱼、叉尾鱼、比目鱼)、硬骨鱼(蓝鲨)；哺乳动物(鲸鱼和抹香鲸)的催乳素；爬行动物(鳄鱼、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)。在调查过程中，我们发现了一种新的脑垂体…更多的蛋白质来自硬骨鱼物种，如大西洋鳕鱼、比目鱼和鲑鱼。对完整氨基酸序列的分析表明，这些蛋白质与生长激素和催乳素有很远或相似的关系。因此，这种属于生长激素催乳素家族新成员的蛋白质被命名为“生长催乳素”。用Fitch和Margoliash方法构建的生长激素分子系统树由四足动物和硬骨鱼两个主干组成。硬骨鱼的躯干比四足动物的躯干大得多，这表明四足动物生长激素在分子进化过程中有更大的保守性。突变的程度与系统发育很好地一致。因此，这些物种的系统发育距离可以通过每100个氨基酸残基的氨基酸变化来半定量。通过序列比对，对生长激素、催乳素和生长激素的进化关系进行了评价。这一估计表明，这些脑下垂体激素由于基因复制而与共同的祖先背道而驰。较少

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