中华鲟生长激素基因的cDNA序列结构与进化分析

Structure and Evolutionary Analysis of Acipenser sinensis Growth Hormone cDNA Sequences

采用RT-PCR方法从中华鲟脑垂体RNA中克隆出645bp的生长激素(growth hormone,GH)cDNA全序列,推导出的GH由214个氨基酸组成,其中前24个氨基酸为信号肽部分。与其它脊椎动物的37个极端保守的氨基酸残基相比,中华鲟有1个氨基酸的差异,即152位上的天冬氨酸变为谷氨酸。中华鲟GH氨基酸保守区可分为5个区域,GD1～GD4区域位于分子外侧,为GH与受体结合区域,与GH活性有关,GD5位于分子内部,与GH分子结构和稳定性有关。中华鲟与俄罗斯鲟的GH序列遗传距离最小,为0.012;与弓鳍鱼、4种哺乳动物和欧洲鳗鲡的遗传距离分别为0.202、0.249～0.260和0.370;而与其它11种硬骨鱼类的遗传距离较大,为0.514～0.601。NJ系统进化树结果显示,中华鲟、俄罗斯鲟、弓鳍鱼、4种哺乳动物和欧洲鳗鲡聚成一支,而其它11种硬骨鱼类聚为另一支。以上结果表明,中华鲟GH与俄罗斯鲟、弓鳍鱼、哺乳动物和欧洲鳗鲡的GH更为相似,而与其它硬骨鱼类的GH同源性较低。

645bp length cDNA that encoded Acipenser sinensis growth hormone （GH） was cloned from pituitary RNA with RT- PCR. The cDNA could encode a prehormone of 214 amino acid （aa） including a putative signal peptide of 24aa. Comparison with 37 amino acid residues highly conserved in other GHs, the Asp was replaced by Glu in the site 152 in A. sinensis mature GH. Alignment analysis indicated that the GH gene was divided into 5 structure domain. GD1 - GD4 domains may be relative to GH activity and specially binding field of receptor, and GD5 domain to molecular structure and stability of the GH. The sequence distance of GH was 0. 012 between A. sinensis and A. gueldenstaedtii, O. 202 between A. sinensis and Amia caiva, O. 249 - 0. 260 between A. sinensis and 4 species of mammalian, 0.370 between A. sinensis and Anguilla anguilla, 0.514 -0. 601 between A. sinensis and the other 11 species of teleostean. Amino acid distance demonstrated that A. sinensis GH had a close genetic relationship with A. gueldenstaedtii, A. caiva, 4 species of mammalian and A. anguilla, while had a far relationship with the other 11 species of teleostean. In mocular phylogenetic tree constructed by NJ method, A. sinensis, A. gueldenstaedtii, A. caiva, 4 species of mammalian and A. anguilla, assembled with a branch, the other 11 species of teleostean assembled another branch. These results indicated that the GH of A. sinensis was similar with that of A. caiva and mammalian, while there was less homogeneity in GH between A. sinensis and teleostean.