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首页> 外文期刊>Infection and immunity >Generation and Surface Localization of Intact M Protein in Streptococcus pyogenes Are Dependent onsagA
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Generation and Surface Localization of Intact M Protein in Streptococcus pyogenes Are Dependent onsagA

机译：化脓性链球菌中完整M蛋白的产生和表面定位取决于sagA

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The M protein is an important surface-located virulence factor of Streptococcus pyogenes, the group A streptococcus (GAS). Expression of M protein is primarily controlled by Mga, a transcriptional activator protein. A recent report suggested that the sag locus, which includes nine genes necessary and sufficient for production of streptolysin S, another GAS virulence factor, is also needed for transcription of emm, encoding the M protein (Z. Li, D. D. Sledjeski, B. Kreikemeyer, A. Podbielski, and M. D. Boyle, J. Bacteriol. 181:6019–6027, 1999). To investigate this in more detail, we constructed an insertion-deletion mutation insagA, the first gene in the sag locus, in the M6 strain JRS4. The resulting strain, JRS470, produced no detectable streptolysin S and showed a drastic reduction in cell surface-associated M protein, as measured by cell aggregation and Western blot analysis. However, transcription of the emmgene was unaffected by the sagA mutation. Detailed analysis with monoclonal antibodies and an antipeptide antibody showed that the M protein in the sagA mutant strain was truncated so that it lacks the C-repeat region and the C-terminal domain required for anchoring it to the cell surface. This truncated M protein was largely found, as expected, in the culture supernatant. Lack of surface-located M protein made the sagA mutant strain susceptible to phagocytosis. Thus, although sagA does not affect transcription of the M6 protein gene, it is needed for the surface localization of this important virulence factor.
机译：M蛋白是链球菌 化脓菌（A群链球菌，GAS）的重要表面定位毒力因子。 M蛋白的表达主要受转录激活蛋白Mga的控制。最近的一份报告表明， sag 基因座包括9个基因，这些基因对于产生链球菌溶血素S（另一种GAS毒力因子）是必需的，而这些基因足以编码 emm ，该基因编码M蛋白（Z. Li，DD Sledjeski，B。Kreikemeyer，A。Podbielski和MD Boyle，J. Bacteriol。181：6019-6027，1999）。为了对此进行更详细的研究，我们在M6株JRS4中的 sag 位点中的第一个基因 sagA 中构建了一个插入-缺失突变。如通过细胞聚集和蛋白质印迹分析所测量的，所得菌株JRS470未产生可检测到的链球菌溶血素S，并显示细胞表面相关M蛋白的急剧减少。但是， emm 基因的转录不受 sagA 突变的影响。用单克隆抗体和抗肽抗体进行的详细分析显示， sagA 突变株中的M蛋白被截短，因此缺少C重复区域和锚定至细胞所需的C末端结构域表面。如所预期的，在培养上清液中主要发现了这种截短的M蛋白。缺乏表面定位的M蛋白使得 sagA 突变株易于吞噬。因此，尽管 sagA 不会影响M6蛋白基因的转录，但此重要毒力因子的表面定位仍需要它。

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