Linkage of T3 and Cpa pilins in the Streptococcus pyogenes M3 pilus.
Linkage of T3 and Cpa pilins in the Streptococcus pyogenes M3 pilus.
复制标题
化脓性链球菌 M3 菌毛中 T3 和 Cpa 菌毛的连锁。
DOI：
10.1111/j.1365-2958.2009.06727.x
复制
发表时间：
2009
影响因子：
3.6
通讯作者：
Scott,JuneR
中科院分区：
文献类型：
--
作者：
Quigley,BernardR;Zahner,Dorothea;Hatkoff,Matthew;Thanassi,DavidG;Scott,JuneR
重要的人类病原体化脓性链球菌（A组链球菌，GAS）通过菌毛介导的对宿主组织的附着启动感染。因此，菌毛是设计抗感染策略的极佳靶点。GAS的T3菌毛由T3蛋白的多个共价连接的亚基组成，两个次要菌毛蛋白Cpa和OrfB共价连接到T3蛋白的亚基。由于GAS皮利的蛋白质不包含其他革兰氏阳性菌中菌毛聚合所需的基序，因此我们研究了参与其连接的残基。我们表明，通过分选酶家族转肽酶SrtC2将Cpa连接到T3需要Cpa细胞壁分选信号中的VPPTG基序。我们还表明，T3的K173是必需的T3聚合和连接的Cpa T3。因此，Cpa与T3亚基的K173的连接将阻止T3亚基进一步添加到生长菌毛的这一端。这意味着Cpa仅位于菌毛尖端，这是免疫金电子显微镜支持的位置，并表明，对于革兰氏阴性菌上研究充分的皮利，菌毛的作用是将粘附素呈递到细菌荚膜外部。
The important human pathogenStreptococcus pyogenes(group A streptococcus, GAS) initiates infection by pilus‐mediated attachment to host tissue. Thus, the pilus is an excellent target for design of anti‐infective strategies. The T3 pilus of GAS is composed of multiple covalently linked subunits of the T3 protein to which the two minor pilins, Cpa and OrfB, are covalently attached. Because the proteins of GAS pili do not contain either of the motifs required for pilus polymerization in other Gram‐positive bacteria, we investigated the residues involved in their linkage. We show that linkage of Cpa to T3 by the sortase family transpeptidase SrtC2 requires the VPPTG motif in the cell wall‐sorting signal of Cpa. We also demonstrate that K173 of T3 is required both for T3 polymerization and for attachment of Cpa to T3. Therefore, attachment of Cpa to K173 of a T3 subunit would block further addition of T3 subunits to this end of the growing pilus. This implies that Cpa is located exclusively at the pilus tip, a location supported by immunogold electron microscopy, and suggests that, as for well‐studied pili on Gram‐negative bacteria, the role of the pilus is to present the adhesin external to the bacterial capsule.