We cloned the MHC- I α gene from cobia (Rachycentron canadium) by homology cloning and RACE PCR. The full-length cDNA of MHC- I α comprises 1 330 bp with a 76 bp 5' untranslated region (UTR), a 189 bp 3' UTR and a 1 065 bp open reading frame (ORF), encoding a polypeptide of 354 amino acid residues with a predicted molecular weight of 40. 10 kDa and a theoretical isoelectric point of 5. 70. According to the phylogenetic tree and amino acid similarity comparison, the homology of MHC- I α amino acids between cobia and some known fishes and human ( Homo sapiens) varies from 27.9％ to 67. 1％. The putative protein sequence shows some important features including leader peptide, αl, α.2, α3, CP/TM/CYT regions and conserved cysteines, etc.. Real-time PCR result indicates that MHC- I α expresses in all detected tissues at different expression levels. High expression is detected in head kidney; moderate expression is detected in gill, spleen and intestine; while low expression is detected in heart, brain and muscle.%采用同源克隆和末端快速扩增(RACE)方法,得到1 330 bp的军曹鱼(Rachycentron canadum)MHC-Ⅰα全长cDNA片段.该序列包括76 bp的5′末端非编码区(UTR),189 bp的3′UTR及1 065 bp的开放阅读框(ORF),编码354个氨基酸,预测其蛋白质分子量约40.10 kDa,等电点5.70.构建MHC-Ⅰα氨基酸序列的系统进化树并进行氨基酸相似性比对,结果表明,军曹鱼和已知鱼类及人类(Homo sapiens)MHC-Ⅰα氨基酸的同源性在27.9%~67.1%之间.所推测的蛋白序列具有一些重要特征,包括前导肽、α1、α2、α3区、CP/TM/CYT区和保守的半胱氨酸等.Real-time PCR检测结果显示,MHC-Ⅰα基因在各个正常军曹鱼组织中均表达,但表达量各有不同,其中较强的表达于头肾;中等程度表达于鳃、脾和肠;在心、脑和肌肉中表达较弱.
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