Identification and Characterization of Hemolysin-Like Proteins Similar to RTX Toxin in Pasteurella pneumotropica
Identification and Characterization of Hemolysin-Like Proteins Similar to RTX Toxin in Pasteurella pneumotropica
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DOI：
10.1128/jb.01527-08
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发表时间：
2009-06-01
影响因子：
3.2
通讯作者：
Yagami, Ken-ichi
中科院分区：
文献类型：
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作者：
Sasaki, Hiraku;Kawamoto, Eiichi;Yagami, Ken-ichi
嗜肺巴氏杆菌是一种条件致病菌，可导致免疫缺陷啮齿类动物致命性肺炎。这种细菌的毒力因子仍然未知。在这项研究中，我们从嗜肺假单胞菌ATCC 35149的基因组DNA中鉴定了编码两种RTX毒素的基因，命名为pnxI和pnxII，并对溶血进行了表征。pnxI操纵子是根据基因编码结构RTX毒素（pnxIA）、I型分泌系统（pnxIB和pnxID）和未知orf的方式组织的。pnxII基因仅与编码结构RTX毒素的pnxIIA有关。推测的PnxIA和PnxIIA的结构RTX毒素都涉及七个RTX重复和重复样序列。通过对嗜肺假单胞菌ATCC 35149中的结构RTX毒素编码基因的定量PCR分析，发现pnxIA的基因表达从早期对数期增加，而pnxIIA的基因表达从晚期对数期增加到早期稳定期。当在大肠杆菌中表达时，PnxIA和PnxIIA的重组蛋白在绵羊和小鼠红细胞中都显示出弱的溶血活性。根据Southern印迹分析的结果，在82%的分离物中检测到pnxIA基因，而在39%的分离物中检测到pnxIIA基因。这些结果表明，pnxIA和pnxIIA的产物都是啮齿动物病原体嗜肺肺疟原虫中毒力因子的推定关联。
Pasteurella pneumotropica is an opportunistic pathogen that causes lethal pneumonia in immunodeficient rodents. The virulence factors of this bacterium remain unknown. In this study, we identified the genes encoding two RTX toxins, designated as pnxI and pnxII, from the genomic DNA of P. pneumotropica ATCC 35149 and characterized with respect to hemolysis. The pnxI operon was organized according to the manner in which the genes encoded the structural RTX toxin (pnxIA), the type I secretion systems (pnxIB and pnxID), and the unknown orf. The pnxII gene was involved only with the pnxIIA that coded for a structural RTX toxin. Both the structural RTX toxins of deduced PnxIA and PnxIIA were involved in seven of the RTX repeat and repeat-like sequences. By quantitative PCR analysis of the structural RTX toxin-encoding genes in P. pneumotropica ATCC 35149, the gene expression of pnxIA was found to have increased from the early log phase, while that of pnxIIA increased from the late log to the early stationary phase. As expressed in Escherichia coli, both the recombinant proteins of PnxIA and PnxIIA showed weak hemolytic activity in both sheep and murine erythrocytes. On the basis of the results of the Southern blotting analysis, the pnxIA gene was detected in 82% of the isolates, while the pnxIIA gene was detected in 39%. These results indicate that the products of both pnxIA and pnxIIA were putative associations of virulence factors in the rodent pathogen P. pneumotropica.