鄱阳湖泥鳅黑色素聚集激素1基因及其蛋白结构特征分析

为研究黑色素聚集激素（Melanin-concentrating hormone，MCH）在泥鳅（Misgurnus anguillicaudatus）皮肤黑色素沉着过程中所起的作用，研究采用RACE-PCR技术首次克隆出了鄱阳湖泥鳅前原黑色素聚集激素1（Prepro-melanin-concentrating hormone 1，Pmch1）基因cDNA全长序列，将其命名为MaPmch1。运用生物信息学软件对MaPmch1基因及其蛋白的理化性质和结构特征进行了分析，构建了系统进化树。其cDNA全长为570 bp，存在一个长度为110 bp的CpG岛，位于263-372 bp；该基因开放阅读框共375 bp，编码含124个氨基酸的蛋白质，共有7个潜在的磷酸化位点；PMCH1蛋白经水解产生17个氨基酸的环形神经肽黑色素聚集激素1（MCH1）。PMCH1和MCH1均为亲水性蛋白，二级结构以无规则卷曲为主；MCH1超二级结构具有一个反平行β-折叠片层，通过二硫键连接形成环形神经肽。同源性分析表明鄱阳湖泥鳅MCH1（MaMCH1）氨基酸序列与其他硬骨鱼类的高度一致。系统进化树显示，包括泥鳅在内的鲤形目PMCH1聚为一支，且物种间PMCH1的亲缘关系与传统的分类地位相吻合。在脊椎动物中，MCH存在高度保守的序列RCM*GRVYRPCW（*代表随机氨基酸），证明该基因在进化上是极为保守的。

STRUCTURE CHARACTERISTICS OF MELANIN-CONCENTRATING HORMONE 1 GENE AND ITS PROTEIN FROMMISGURNUS ANGUILLICAUDATUS

Melanin-concentrating hormone (MCH) played an important role in the process of skin melanin pigmenta-tion. In order to known its characteristics and founction, the cDNA sequence of the MCH (refers toMaPmch1) from loach of the Poyang Lake was first cloned by RACE-PCR. Bioinformatics approaches were used to analyze physico-chemical property, conserved domains, secondary structures, homologous analysis and phylogenetic tree. The full length ofMaPmch1 gene was 570 bp that contained an open reading frame of 375 bp encoding 124 amino acid residues. A CpG island with the length of 110 bp in the cDNA sequence ofMaPmch1was located in 263—372 bp. It was predicted that the MaPMCH1 contained seven potential phosphorylation sites. A 17-AA-amidated cyclic neuropeptide named MaMCH1 was generated from MaPMCH1 after hydrolyzing. MaPMCH1 and MaMCH1 were pre-dicted to be hydrophilic proteins mainly contained random coil for their secondary structures. The super secondary structure of MaMCH1 with anantiparallel β-plated sheet, was connected by a disulfide bond. Homology analysis indi-cated that the amino acid sequence of MaMCH1 was highly conserved with other bony fishes. The phylogenetic tree showed that MaPMCH1 and Cyprinid fish’s PMCH1 were in the same branch, and the genetic relationship of PMCH1 was conserved with the traditional classification status. In vertebrate, RCM*GRVYRPCW (* as random amino acid) was a highly conserved sequence, suggesting thatPmch1 gene was highly conserved during the evolution.