Assembly of pili on the surface of Corynebacterium diphtheriae
Assembly of pili on the surface of Corynebacterium diphtheriae
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DOI：
10.1046/j.1365-2958.2003.03782.x
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发表时间：
2003-11-01
影响因子：
3.6
通讯作者：
Schneewind, O
中科院分区：
文献类型：
--
作者：
Ton-That, H;Schneewind, O
革兰氏阴性病原体的皮利由菌毛蛋白前体分子通过外膜包膜内的非共价缔合形成。革兰氏阳性微生物利用细胞壁肽聚糖作为表面细胞器用于蛋白质的共价附着，然而，皮利的组装途径尚未被揭示。白喉棒状杆菌的皮利由SpaA、SpaB和SpaC三个菌毛蛋白亚基组成。主要的菌毛蛋白SpaA沿着菌毛轴均匀分布，而SpaB以规则的间隔观察，SpaC似乎位于菌毛尖端。组装的皮利通过用胞壁蛋白水解酶处理而从细菌表面释放，这表明菌毛纤维可能被锚定到细胞壁被膜。所有三种菌毛蛋白亚基蛋白作为携带N-末端信号肽和C-末端分选信号的前体合成。在C.白喉需要用于前体加工、菌毛组装或细胞壁包膜附着。菌毛组装被认为是通过有序交联的机制发生的，由此菌毛蛋白特异性分选酶在分选信号处切割前体蛋白，并涉及菌毛蛋白基序序列的侧链氨基以产生菌毛蛋白亚基之间的连接。这种相邻菌毛蛋白亚基的共价束缚似乎已经在许多革兰氏阳性病原体中进化，所述革兰氏阳性病原体编码具有分选信号和菌毛蛋白基序的分选酶和菌毛蛋白亚基基因。
Pili of Gram-negative pathogens are formed from pilin precursor molecules by non-covalent association within the outer membrane envelope. Gram-positive microbes employ the cell wall peptidoglycan as a surface organelle for the covalent attachment of proteins, however, an assembly pathway for pili has not yet been revealed. We show here that pili of Corynebacterium diphtheriae are composed of three pilin subunits, SpaA, SpaB and SpaC. SpaA, the major pilin protein, is distributed uniformly along the pilus shaft, whereas SpaB is observed at regular intervals and SpaC seems positioned at the pilus tip. Assembled pili are released from the bacterial surface by treatment with murein hydrolase, suggesting that the pilus fibres may be anchored to the cell wall envelope. All three pilin subunit proteins are synthesized as precursors carrying N-terminal signal peptides and C-terminal sorting signals. Some, but not all, of the six sortase genes encoded in the genome of C. diphtheriae are required for precursor processing, pilus assembly or cell wall envelope attachment. Pilus assembly is proposed to occur by a mechanism of ordered cross-linking, whereby pilin-specific sortase enzymes cleave precursor proteins at sorting signals and involve the side chain amino groups of pilin motif sequences to generate links between pilin subunits. This covalent tethering of adjacent pilin subunits appears to have evolved in many Gram-positive pathogens that encode sortase and pilin subunit genes with sorting signals and pilin motifs.