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首页> 外文期刊>Infection and immunity >Mode of Expression and Functional Characterization of FCT-3 Pilus Region-Encoded Proteins in Streptococcus pyogenes Serotype M49
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Mode of Expression and Functional Characterization of FCT-3 Pilus Region-Encoded Proteins in Streptococcus pyogenes Serotype M49

机译：化脓性链球菌M49血清型FCT-3毛孔区编码蛋白的表达方式和功能表征

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The human pathogen Streptococcus pyogenes (group A streptococcus [GAS]) pilus components, suggested to play a role in pathogenesis, are encoded in the variable FCT (fibronectin- and collagen-binding T-antigen) region. We investigated the functions of sortase A (SrtA), sortase C2 (SrtC2), and the FctA protein of the most prevalent type 3 FCT region from a serotype M49 strain. Although it is considered a housekeeping sortase, SrtA's activity is involved in pilus formation in addition to its essentiality for GAS extracellular matrix protein binding, host cell adherence/internalization, survival in human blood, and biofilm formation. SrtC2 activity is crucial for pilus formation but dispensable for the other phenotypes tested in vitro. FctA is the major pilus backbone protein, simultaneously acting as the M49 T antigen, and requires SrtC2 and LepA, a signal peptidase I homologue, for monomeric surface expression and polymerization, respectively. Collagen-binding protein Cpa expression supports pilus formation at the pilus base. Immunofluorescence microscopy and fluorescence-activated cell sorting analysis revealed several unexpected expression patterns, as follows: (i) the monomeric pilus protein FctA was found exclusively at the old poles of GAS cells, (ii) FctA protein expression increased with lower temperatures, and (iii) FctA protein expression was restricted to 20 to 50% of a given GAS M49 population, suggesting regulation by a bistability mode. Notably, disruption of pilus assembly by sortase deletion rendered GAS serotype M49 significantly more aggressive in a dermonecrotic mouse infection model, indicating that sortase activity and, consequently, pilus expression allow a subpopulation of this GAS serotype to be less aggressive. Thus, pilus expression may not be a virulence attribute of GAS per se.
机译：提示人类病原体化脓性链球菌（A群链球菌[GAS]）菌毛成分在可变FCT（纤连蛋白和胶原结合性T抗原）区域编码。我们调查了血清型M49菌株中最普遍的3型FCT区的分选酶A（SrtA），分选酶C2（SrtC2）和FctA蛋白的功能。尽管它被认为是管家分类酶，但SrtA的活性除了对GAS细胞外基质蛋白结合，宿主细胞粘附/内在化，人血液中的存活以及生物膜形成的必要性外，还参与菌毛的形成。 SrtC2活性对于菌毛形成至关重要，但对于体外测试的其他表型则是必不可少的。 FctA是主要的菌毛骨架蛋白，同时充当M49 T抗原，并且分别需要SrtC2和LepA（信号肽酶I同源物）用于单体表面表达和聚合。胶原蛋白结合蛋白Cpa的表达支持菌毛在菌毛基部的形成。免疫荧光显微镜和荧光激活的细胞分选分析揭示了以下几种出乎意料的表达模式：（i）单体菌毛蛋白FctA仅在GAS细胞的老两极发现，（ii）FctA蛋白表达随温度降低而增加，和（ iii）FctA蛋白表达仅限于给定GAS M49人群的20％至50％，表明是通过双稳态模式进行调节。值得注意的是，分选酶缺失对菌毛组装的破坏使GAS血清型M49在皮肤坏死性小鼠感染模型中更具侵略性，表明分选酶活性以及菌毛表达使该GAS血清型的亚群侵袭性降低。因此，菌毛的表达本身可能不是GAS的毒力属性。

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