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诺卡氏菌(Nocardia seriolae)是近年来海淡水养殖鱼类频发慢性传染病的病原菌。该研究通过引物扩增得到全长1 254 bp、编码417个氨基酸的诺卡氏菌毒力因子mce1A基因的全序列。该基因编码蛋白质的分子量约为43.98 k D,理论等电点5.14,含有161个疏水性氨基酸,疏水性平均值为0.044,为疏水性蛋白,具有α-螺旋、β-折叠和无规则卷曲3种结构。经预测,Mce1A有MCE、DUF3407区域、OM_asym_Mla D、Mtu_fam_mce、Mla D 5个结构域,彼此交叠,含有公共区域。根据Mce1A氨基酸构建的系统进化树可以发现诺卡氏菌和新星诺卡氏菌的亲缘关系最近。构建p ET32a-mce1A重组质粒并转化至大肠埃希菌BL21中,得到的重组蛋白的相对分子量约63 k D。温度、IPTG浓度对重组蛋白表达量没有影响。该研究为进一步研究Mce1A的致病机制奠定了基础。
Nocardia seriolae is a pathogen that causes frequent chronic infectious diseases in freshwater fish in recent years. In this study, a full-length cDNA sequence of 1 254 bp encoding the 417 amino acid sequence of the virulence factor mce1A was obtained by primer amplification. The gene encodes a protein with a molecular weight of about 43.98 kD, a theoretical isoelectric point of 5.14 and contains 161 hydrophobic amino acids with an average hydrophobicity of 0.044 and is a hydrophobic protein with alpha-helix, beta-sheet, and random coil 3 Structure. It is predicted that Mce1A has MCE, DUF3407 region, OM_asym_Mla D, Mtu_fam_mce, and Mla D 5 domains overlapping each other and containing the common region. According to the phylogenetic tree constructed by Mce1A amino acids, it is found that the relationship between Nocardia nocardia and Nocardia innocua is the closest. The recombinant plasmid p ET32a-mce1A was constructed and transformed into Escherichia coli BL21. The relative molecular weight of the resulting recombinant protein was about 63 kD. Temperature and IPTG concentration had no effect on the recombinant protein expression. This study laid the foundation for further study on the pathogenesis of Mce1A.