采用RT-PCR和cDNA末端快速扩增法(RACE)分离、克隆出鲇(Parasilurus asotus)垂体阿黑皮素原(proopiomelanocortin,POMC)基因全长cDNA序列,共1 099 bp,包括129 bp 5’非翻译区、648 bp阅读框以及322 bp3′非翻译区,阅读框共编码215个氨基酸,POMC前体蛋白的结构主要由信号肽(Met1-Ala28)、N端多肽(Gln29-Asp102)、促肾上腺皮质激素(ACTH,Ser105-Met144)、a-黑色素细胞刺激激素(a-MSH,Ser105-Val 117)、促肾上腺皮质激素样中叶肽(CLIP,Arg123-Met144)、γ-促脂解激素(γ-LPH,Glu145-Ser158)、β-黑色素细胞刺激激素(β-MSH,Asp161-Ser177)和β-内啡肽(β-EP,Tyr178-Leu215)构成.分子量计算值为24.66kD,理论等电点为7.25.同源性分析表明鲇与斑点叉尾(鲴)的相似性高达88％,其构成多肽中a-MSH、β-MSH、β-EP、CLIP保守性逐渐降低,而γ-MSH、连接肽(JP)、γ-LPH是变异比较大的区域,同时鲇POMC中不含有γ-MSH,连接肽和部分γ-LPH也不存在.生物信息学分析显示鲇POMC基因所编码的蛋白质以亲水性区域为主,具有丰富的B细胞抗原位点.定量分析结果表明POMC mRNA主要在垂体中高表达,在非垂体组织的脑中表达量最高,鳃、头肾、肝、脾、肌肉、皮肤等组织也有少量表达.%We investigated the structure, evolution, and tissue specific expression of Parasilurus asotus proopiomelanocortin (POMC) cDNA using RT-PCR and RACE. The POMC cDNA was 1 099 bp in length and contained a 129 bp 5'UTR, a 322 bp 3'UTR, and a 648 bp open reading frame encoding a protein of 215 amino acids. The catfish POMC protein contained a signal peptide (SP, Met1-Ala28), an N-terminal peptide (Gln29-Asp102), adrenocorticotropic hormone (ACTH, Ser105-Met144), α-melanocyte stimulating hormone (α-MSH, Ser105-Val117), corticotropin-like intermediate lobe peptide (CLIP, Arg123-Met144), β-lipotropin (β-LPH, Glu145-Ser158), β-MSH (Asp161-Ser177), and β-Endorphin (β-EP, Tyr178-Leu215). Catfish POMC protein does not contain a γ-MSH region and the majority of the joining peptide and part of the γ-LPH were deleted. The protein shared the highest similarity (88%) with channel catfish {Parasilurus asotus) POMC. The most highly conserved active peptide was α-MSH, followed by β-MSH, β-EP, and CLIP whereas γ-MSH, joining peptide (JP), and γ-LPH were located in the most divergent region. The protein had a calculated molecular weight of 24.66 kD, a theoretical isoelectric point of 1.25, was hydrophilic in most regions, and was rich in B cell antigenicity positions. Catfish POMC mRNA was primarily expressed in the pituitary and the concentration of mRNA was much higher in brain than in other tissues.
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