Takeuchi S, Kudo T, Takahashi S
Department of Biology, Faculty of Science, Okayama University, Okayama 700, Japan.
Biochim Biophys Acta. 1998 May 27;1403(1):102-8. doi: 10.1016/s0167-4889(98)00022-6.
The chicken melanocortin 2-receptor (MC2-R) gene was isolated. It is found to be a single copy gene encoding a 357 amino acid protein, sharing 65.8-68.7% identity with mammalian counterparts. The chicken MC2-R mRNA is expressed in the adrenal and spleen, suggesting that the receptor mediates both endocrine and immunoregulatory functions of ACTH in the chicken. The amino acid sequence of the chicken MC2-R is collinear with those of other subtypes of MC-R, whereas all cloned mammalian MC2-Rs contain a gap in the third intracellular loop, suggesting that mammalian MC2-R molecules have evolved by lacking a part of the domain which determines the specificity of signal transduction in G-protein coupled receptors. Interestingly, the codon usage differs dramatically between MC1-R and MC2-R in the chicken; the GC-contents at the third codon position in MC1-R and MC2-R are 94.6 and 50.6%, respectively. It may reflect selective constraints on the usage of synonymous codons.
鸡促黑素皮质素2受体（MC2-R）基因被分离出来。它是一个单拷贝基因，编码一种含357个氨基酸的蛋白质，与哺乳动物的对应物具有65.8 - 68.7%的同源性。鸡MC2-R mRNA在肾上腺和脾脏中表达，这表明该受体介导了促肾上腺皮质激素（ACTH）在鸡体内的内分泌和免疫调节功能。鸡MC2-R的氨基酸序列与MC-R的其他亚型共线，而所有克隆的哺乳动物MC2-Rs在第三个细胞内环中都有一个缺口，这表明哺乳动物MC2-R分子在进化过程中缺失了一部分决定G蛋白偶联受体信号转导特异性的结构域。有趣的是，鸡的MC1-R和MC2-R之间密码子使用差异很大；MC1-R和MC2-R第三个密码子位置的GC含量分别为94.6%和50.6%。这可能反映了对同义密码子使用的选择性限制。
