Smyth C J, Marron M B, Twohig J M, Smith S G
Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, University of Dublin, Ireland.
FEMS Immunol Med Microbiol. 1996 Dec 1;16(2):127-39. doi: 10.1111/j.1574-695X.1996.tb00129.x.
Fimbriae are wiry (2 to 4 nm diam.) or rod-shaped (6 to 8 nm diam.), fibre-like structures on the surfaces of bacteria which mediate attachment to host cells. Much has been learned in recent years about the biogenesis, structure and regulation of expression of these adhesive organelles in Gram-negative bacteria. Analyses of the genetic determinants encoding the biogenesis of fimbriae has revealed that the adhesive interaction of fimbriae can be mediated by major subunits (CFA/I and CS1 fimbriae) or minor subunits (P, S, and type 1 fimbriae), with the adhesin being located either at the tip of the fimbria or along the length of the fimbrial shaft. Minor subunits can also act as adapters, anchors, initiators or elongators. Post-translational glycosylation of the type 4 pilins of Neisseria gonorrhoeae, Neisseria meningitidis and Pseudomonas aeruginosa has been demonstrated. The structures of the PapD chaperone of Escherichia coli and of N. gonorrhoeae type 4 fimbrin have been resolved at 2.0-2.6 A. Rod-shaped fimbriae should not be thought of as being rigid inflexible structures but rather as dynamic structures which can undergo transition from a helicoidal to a fibrillar conformation to provide a degree of elasticity and plasticity to the fimbriae so that they can resist shear forces, rather like a bungee cord. At least four mechanisms have been identified in the assembly of fimbriae from fimbrin subunits, namely the chaperone-usher pathway (e.g., P-fimbriae of uropathogenic E. coli), the general secretion assembly pathway (e.g., type 4 fimbriae or N-methylphenylalanine fimbriae of P. aeruginosa, the extracellular nucleation-precipitation pathway (e.g., curli of E. coli) and the CFA/I, CS1 and CS2 fimbrial pathway.
菌毛是丝状的（直径2至4纳米）或杆状的（直径6至8纳米），是细菌表面的纤维状结构，介导细菌与宿主细胞的附着。近年来，人们对革兰氏阴性菌中这些粘附细胞器的生物合成、结构和表达调控有了很多了解。对编码菌毛生物合成的遗传决定因素的分析表明，菌毛的粘附相互作用可由主要亚基（CFA/I和CS1菌毛）或次要亚基（P、S和1型菌毛）介导，粘附素位于菌毛尖端或菌毛轴的长度方向上。次要亚基还可作为衔接蛋白、锚定蛋白、起始蛋白或延伸蛋白。已证实淋病奈瑟菌、脑膜炎奈瑟菌和铜绿假单胞菌的4型菌毛蛋白存在翻译后糖基化。大肠杆菌的PapD伴侣蛋白和淋病奈瑟菌4型菌毛蛋白的结构已在2.0 - 2.6埃的分辨率下解析出来。杆状菌毛不应被视为刚性的、不可弯曲的结构，而应被视为动态结构，它可以从螺旋状构象转变为纤维状构象，为菌毛提供一定程度的弹性和可塑性，使其能够抵抗剪切力，有点像蹦极绳。从菌毛蛋白亚基组装菌毛至少已确定了四种机制，即伴侣-usher途径（例如，尿路致病性大肠杆菌的P菌毛）、一般分泌组装途径（例如，铜绿假单胞菌的4型菌毛或N-甲基苯丙氨酸菌毛）、细胞外成核-沉淀途径（例如，大肠杆菌的卷曲菌毛）以及CFA/I、CS1和CS2菌毛途径。
