Shibahara S, Kubo T, Perski H J, Takahashi H, Noda M, Numa S
Eur J Biochem. 1985 Jan 2;146(1):15-22. doi: 10.1111/j.1432-1033.1985.tb08614.x.
Human genomic DNA encoding the gamma subunit precursor of the skeletal muscle acetylcholine receptor has been cloned by screening a gene library with a calf cDNA probe and has been subjected to nucleotide sequence analysis. Comparison of the nucleotide sequence of the cloned human genomic DNA with that of the calf cDNA has revealed that the protein-coding sequence of this gene is divided by 11 introns into 12 exons. Evidence is presented to suggest that the human muscle acetylcholine receptor gamma and delta subunit genes are juxtaposed. The primary structure of the gamma subunit precursor of the human muscle acetylcholine receptor has been deduced from the corresponding gene sequence. This polypeptide is composed of 517 amino acids including a hydrophobic prepeptide of 22 amino acids. The gamma subunit of the human muscle acetylcholine receptor, like the alpha subunit of the same receptor as well as the alpha, beta and gamma subunits of its calf counterpart, shares structural features common to all four subunits of the Torpedo electroplax receptor, such as the putative disulphide bridge corresponding to that in the alpha subunit proposed as being in close proximity to the acetylcholine binding site and the four putative, hydrophobic transmembrane segments M1-M4. Thus, the human gamma subunit molecule apparently exhibits the same transmembrane topology as proposed for the fish receptor subunits. The 12 exons seem to correspond to different structural and functional domains of the gamma subunit precursor molecule. Some exons and the protein regions encoded by them are more highly conserved between the mammalian and Torpedo sequences. The pattern of regional homology observed is consistent with the relatively high conservation of the region encompassing the putative disulphide bridge and of the region containing the putative transmembrane segments M1, M2 and M3.
通过用小牛cDNA探针筛选基因文库，已克隆出编码骨骼肌乙酰胆碱受体γ亚基前体的人类基因组DNA，并对其进行了核苷酸序列分析。将克隆的人类基因组DNA的核苷酸序列与小牛cDNA的核苷酸序列进行比较，结果表明该基因的蛋白质编码序列被11个内含子分隔为12个外显子。有证据表明人类肌肉乙酰胆碱受体γ和δ亚基基因是并列的。已从相应的基因序列推导出人类肌肉乙酰胆碱受体γ亚基前体的一级结构。该多肽由517个氨基酸组成，包括一个22个氨基酸的疏水前肽。人类肌肉乙酰胆碱受体的γ亚基，与其相同受体的α亚基以及小牛对应物的α、β和γ亚基一样，具有与电鳐电板受体所有四个亚基共有的结构特征，例如与α亚基中被认为紧邻乙酰胆碱结合位点的二硫键相对应的假定二硫键，以及四个假定的疏水跨膜片段M1 - M4。因此，人类γ亚基分子显然呈现出与鱼类受体亚基所提出的相同的跨膜拓扑结构。这12个外显子似乎对应于γ亚基前体分子的不同结构和功能域。在哺乳动物和电鳐序列之间，一些外显子及其编码的蛋白质区域具有更高的保守性。观察到的区域同源性模式与包含假定二硫键的区域以及包含假定跨膜片段M1、M2和M3的区域的相对高保守性一致。
