【摘要】 为了深入地了解胸膜肺炎放线杆菌(APP)分泌的ApxⅡ毒素的分子结构及序列特征,本实验以一株APP 7型现地分离株L25-4株为实验材料,对其分泌的ApXⅡ毒素的结构基因apxⅡA及其上游启动子区进行了PCR扩增和测序。结果表明APP7型L25-4株apxⅡA基因与其它血清型apxⅡA基因核苷酸序列同源性达99．5%以上,氨基酸序列同源性达98．5%以上。在ApxⅡA蛋白的N末端有3个大的疏水结构域,分布在240～422位氨基酸之间。在ApxⅡA蛋白的C末端有富含甘氨酸(Gly)和天门冬氨酸(Asp)的九肽(nonapeptides)重复序列Leu/Ile/Phe-Xaa-Gly-Gly-Xaa-Gly-Asm/Ssp-Asp-Xaa,串连重复9次。这些结构域的起始氨基酸的位置分别为374、503、630、735、753、762、771、780和802。推定的赖氨酸酰基化作用位点为557位氨基酸,与E．coli的HlyA相比,在688位氨基酸处少了一个赖氨酸酰基化作用位点。apxⅡA基因启动子-10区序列为AATAAT,-35区序列为TTAAT,-10区与-35区间隔序列为11个碱基。更多还原

【Abstract】 In order to deeply understand the structure and molecular pathogenesis of ApxⅡtoxin of Actinobacillus pleuropneumoniae,the stucture gene apxⅡA of ApxⅡtoxin of Actinobacillus pleuropneumoniae serotype 7 strain L25-4 was amplified by PCR and sequenced as well as the promoter gene upstream.The result showed that the nucleotide and amino acid homogeneity of serotype 7 strain L25-4 with other serotypes are 99.5% and 98.5%,respectively.There are three large hydrophobic domains at N’-terminal part of ApxⅡA,they located between 240-422 amino acid.A typical nonapeptides repeats domain was found at C’-terminal part of ApxⅡA which riches in Gly and Asp,Leu/Ile/Phe-Xaa-Gly-Gly-Xaa-Gly-Asm/Ssp- Asp-Xaa repeats for 9 times within ApxⅡA.The initial sites of the repeated domains are 374,503,630,735,753,762, 771,780 and 802,respectively.The putative Lys acylation site(GK)of ApxlIA is 557 amino acid,however,there is a deletion of GK at 688 amino acid compared with E.coli HlyA.The sequence of-10 region of apxⅡA promoter is AATAAT,-35 region is TTAAT,there are 11 bases within the spacer between-10 and-35 region.更多还原