Functional analysis of adhesins and colonization factors produced by human pathogenic streptococci

人类病原体化脓性链球菌根据不同的血清型产生不同的菌毛。在一株M49型化脓性链球菌中，我们证明了FctA是菌毛骨架蛋白，而FctB和CpA是一种胶原结合粘附素，是辅助蛋白。我们还发现，CPA和FctA都是胰酶抗性T抗原。突变试验和真核细胞黏附试验表明，FctB和看家分类酶SrtA有助于菌毛的细胞壁锚定，而CPA则作为菌毛与角质形成细胞的粘附素。山梨酸酶C2和可能的信号肽酶LEPA是FctA聚合的关键酶。菌毛的表达随着温度的降低而增加。形成生物膜的能力不受菌毛基因突变的影响。与M49菌毛不同，M6型化脓性链球菌菌毛由两种蛋白质组成，即主干蛋白T6和辅助蛋白FctX，这种方式既需要SrtA，也需要菌毛相关的分类酶SrtB。我们发现，在本研究使用的条件下，T6菌毛有助于生物膜的形成，但不有助于粘附人角质形成细胞。这些数据提示化脓性链球菌菌毛的血清型依赖的菌毛组装机制和对组织趋向性的贡献。

The human pathogen Streptococcus pyogenes produces diverse pili depending on the serotype. In a serotype M49 S. pyogenes strain, we demonstrate that FctA is the pilus backbone protein, and FctB and Cpa, a collagen-binding adhesin, are ancillary proteins. We also found that both Cpa and FctA are trypsin-resistant T antigens. Mutagenesis assays and eukaryotic cell adherence tests revealed that FctB and housekeeping sortase SrtA contribute to the cell wall anchoring of pili, whereas Cpa functions as a pilus adhesin to human keratinocytes. Sortase C2 and putative signal peptidase LepA enzymes were crucial for polymerization of FctA. The pilus expression increased with lower temperature. The ability to form biofilms was not affected by the mutation of the pilus genes. In contrast to the M49 pili, pili of a serotype M6 S. pyogenes strain were found to be assembled from two proteins, i.e. the backbone protein T6 and ancillary protein FctX, in a manner that requires both SrtA and pilus-associated sortase SrtB. We found that T6 pili contribute to biofilm formation, but not to adherence to human keratinocytes under the condition used in this study. These data suggest the serotype-dependent pilus assembly mechanism and contribution of S. pyogenes pili to the tissue tropism.