猪链球菌ZKHY株gdh基因的克隆与序列分析

Cloning and Sequence Analysis of the Gene Encoding Glutamate Dehydrogenase of Streptococcus suis Strain ZKHY

对猪链球菌ZKHY株的谷氨酸脱氢酶基因（gdh）进行克隆和序列分析，以ZKHY株的基因组DNA为模板，采用PCR方法扩增出谷氨酸脱氢酶基图片段，克隆于pMD-18T载体，转化宿主菌JM109中进行序列测定。将测序结果与GenBank已登录序列进行核苷酸和氨基酸的同源性分析。序列分析显示，成功克隆了猪链球菌ZKHY株的gdh基因，ZKHY与已报道的猪链球菌gdh基因有密切的亲缘关系，核酸序列与血清2、7、9型的同源性为97．2％～98．4％，其中与2型菌株同源性为97．2％～97．3％；与7型菌株同源性为98．4％；与9型菌株同源性为97．6％。其编码的氨基酸序列同源性则更高，与GenBank中已收录的序列同源性在98．9％以上。ZKYH株可能是属于2、7、9型之外的其他血清型；所克隆的基因在猪链球菌之中非常保守，可以进行表达以用作免疫学方面的相关研究。

In order to study the function of the protein of glutamate hydrogenase （GDH）, the glutamate dehydrogenase gene of Streptococcus suis strain ZKHY was cloned and analyzed in this pa per. The g dh gene was amplified by polymerase chain reaction （PCR） and cloned into pMD - 18T vector. After transformed into E. coli JM109 competent cells, the recombinant plasmid was se quenced and compared with the nucleotide and deduced amino acid sequences of previous reported strains in GenBank. The results showed that the sequence has close relationship to the gdh gene of Streptococcus suis published in GenBank, which has sequence homology of 97.2%--97.3%, 98.4% and 97.6% with serotype 2, 7 or 9 strains, respectively. Especially, the homology of amino acid sequence was even higher than that of nucleotide sequence, which is above 98.9%. This indicates that strain ZKHY may be out of serotypes 2, 7 and 9. The gene cloned in this study is very conservativea and it can be expressed in prokaryotic or eukaryotic cells for imrnunology-concerned researches.