牦牛IGF-IR基因克隆及其序列分析

Cloning and Sequence Analysis of Yak IGF-IR Gene

为研究牦牛胰岛素样生长因子1受体基因(IGF-IR)的结构和功能,采用同源克隆和RT-PCR方法分段扩增牦牛IGF-IR,拼接获得全长序列,利用生物学软件进行分析。结果表明,牦牛IGF-IR基因ORF长约4 104 bp,编码1 367个氨基酸;理论分子量约154. 95 ku,等电点p I值约5. 71。与黄牛IGF-IR比较,牦牛IGF-IR基因序列有20处碱基改变,其中G到T碱基颠换2次,G到A碱基转换2次,C到T碱基转换7次,A到G碱基转换3次,T到C碱基转换6次,以及3个位点氨基酸改变(G6R、T29I和S30I)。系统进化分析表明,牦牛与黄牛、猪、人、狗、小鼠、猩猩等物种IGF-IR氨基酸相似性均大于92%,处于同一进化分支,具有高度同源性。蛋白结构预测表明,牦牛IGF-IR包含半胱氨酸富集区(FU)、纤连蛋白Ⅲ型结构域(FN3)、跨膜结构域(TM)及酪氨酸蛋白激酶区(Tyr Kc),具有该受体家族的特征结构域。同源建模表明,其成熟区段氨基酸序列与人的IGF-IR有98. 68%的相似性。为后续牦牛IGF-IR基因的功能研究奠定了基础。

The complete cDNA encoding yak insulin like growth factor 1 receptor （IGF-IR） gene was cloned with RT-PCR and homologous cloning methods. Sequence analysis showed that the entire coding region was 4 104 bp in length encoding 1 367 amino acids with a putative mass of 154.95 ku and pI of 5.71. Compared to IGF-IR gene sequence from cattle, there were 20 base changes in yak IGF-IR gene, including 2 substitutions for G-T, 2 transitions for G-A, 7 transitions for C-T, 3 transitions for A-G and 6 transitions for T-C, respectively. In addition, amino acid changed at 3 sites （G6R, T29I and S30I）. The phylogenetic analysis revealed that yak IGF-IR gene had high homology （〉 92%）with that of cattle, pig, human, dog, mouse and chimpamzee, which were classified into the same branch. The secondary structure predication indicated that yak IGF-IR protein might have the typical domains of the IGF-IR family, containing the furin-like cysteine rich region （FU）, fibronectin type Ⅲ domain （FN3）, transmembrane domain （TM）, and tyrosine kinase domain （TyrKc）, respectively. 3D model showed the mature fragment in yak IGF-IR had 98.68% homology with human IGF-IR. The present results provided the valuable foundation for further studies on yak IGF-IR functions.