猪黑皮质素受体3和4基因克隆及分析

Molecular cloning and analysis and tissue distribution of melanocortin receptor 3 and 4 genes in pigs(Sus scrofa)

以长白猪(Landrace)大脑cDNA为模板,克隆长白猪黑皮质素受体3和4基因(MC3R和MC4R).序列分析显示:长白猪MC3R基因cDNA编码具319个氨基酸的前体蛋白,与人、大鼠、小鼠和斑马鱼的氨基酸序列一致性分别为86.4%、83.3%、82%和69.7%;MC4R基因cDNA全长1175bp,编码具332个氨基酸的前体蛋白,与人、大鼠、小鼠的氨基酸序列一致性高达94%以上,与斑马鱼MC4R氨基酸序列享有70.7%的同源性.序列分析显示,猪MC3R和MC4R基因都具有典型的七次跨膜结构域,和短的胞内环和胞外环,且在第五个跨膜域中保守的甲硫氨酸(M)分别替换为异亮氨酸(I)和缬氨酸(V).另外,在猪MC3R和MC4R中还鉴定到保守的半胱氨酸残基,第一个胞内环中保守的PMY基序和N末端的3个N-链接糖基化位点.组织表达图谱分析表明,MC3R主要在大脑和脾中高表达,而MC4R主要在六种检测的组织中都有表达,在肾中表达较弱.

Abstract. In this study, using eDNA of Landrace pig brain as the template, the full-length cDNAs of MC3R and MC4R genes have been cloned. Pig MC3R eDNA encodes a protein precursor of 319 amino acids, which shares high amino acid sequence identity with that of human （86. 4%）, rat （83. 3%）, mouse （82%） and zebrafish（69.7%）. Pig MC4R eDNA is 1175 bp in length and encodes a protein pre- cursor of 332 amino acids, which shares high amino acid sequence identity （〉94%） with that of mam- mals and zebrafish（69.7 %）. Further structural analyses indicate that pig MC3R and MC4R contain typi- cal seven transmembrane domains and short extracellular （ECL） and intracellular （ICL） loops. The sub- stitution of a methionine for isoleucine（MC3R）/ Valine（MC4R） in the fifth transmembrane domain （TMD 5） also has been identified. In addition, pig MC3R and MC4R share the PMY motif in the first ICL and 3 conserved N-linked glycosylation sites within N-terminal domain which are conserved in most MCRs. RT-PCR assay revealed that. MC3R is mainly expressed in brain and spleen with high abun- dance. While MC4R is expressed all six pig tissues examined with relatively weak signals in kidney.