Identification of the region in the hCG cDNA associating its bioactivity by using biotechnology

人绒毛膜促性腺激素(HCG)、促黄体生成素(LH)、促甲状腺激素(TSH)和卵泡刺激素(FSH)由两个非共价连接的亚基组成，即α和β亚基。β亚基对每种激素都是特定的，并负责生物特异性，但不同激素的β亚基在结构上显示出一定程度的同源性。CAGY(半胱氨酸-丙氨酸-甘氨酸-酪氨酸)区是不同β亚基中同源的氨基酸序列之一，在物种间高度保守。在本研究中，我们使用体外定点突变技术改变了hCGβ亚基cagy区中心的三个核苷酸，并通过体外转录和翻译来确定这些突变对非洲爪哇卵母细胞产生hCG的影响。结果表明，cagy区，尤其是β亚基36位的甘氨酸残基是hCG产生所必需的。这一发现与之前的研究一致，表明该区域是HTSH生物活性所必需的。

The heterodimeric glycoprotein hormones, hCG, LH, TSH and FSH consist of two noncovalently linked subunits, the alpha and beta subunits. The beta subunit is specific for each hormone and is responsible for the biological specificity, but the beta subunits of different hormones show some degree of structural homology. The CAGY (cysteine-alanine-glycine-tyrosine) region is one of the amino acid sequences that is homologous in different beta subunits and is highly conserved beyond species. In the present study, we used site-specific in vitro mutagenesis to change three individual nucleotides in the center of the CAGY region of the hCG beta subunit, and determined the effects of these mutations on hCG production by in vitro transcription and then translation in Xenopus oocytes. The results indicated that the CAGY region, particularly the glycine residue at position 36 in the beta subunit, is essential for the production of hCG. This finding is consistent with previous studies showing that this region is necessary for the biological activity of hTSH.