Forest K T, Dunham S A, Koomey M, Tainer J A
Department of Molecular Biology, Scripps Research Institute, La Jolla, CA 92037, USA.
Mol Microbiol. 1999 Feb;31(3):743-52. doi: 10.1046/j.1365-2958.1999.01184.x.
Understanding the structural biology of type IV pili, fibres responsible for the virulent attachment and motility of numerous bacterial pathogens, requires a detailed understanding of the three-dimensional structure and chemistry of the constituent pilin subunit. X-ray crystallographic refinement of Neisseria gonorrhoeae pilin against diffraction data to 2.6 A resolution, coupled with mass spectrometry of peptide fragments, reveals phosphoserine at residue 68. Phosphoserine is exposed on the surface of the modelled type IV pilus at the interface of neighbouring pilin molecules. The site-specific mutation of serine 68 to alanine showed that the loss of the phosphorylation alters the morphology of fibres examined by electron microscopy without a notable effect on adhesion, transformation, piliation or twitching motility. The structural and chemical characterization of protein phosphoserine in type IV pilin subunits is an important indication that this modification, key to numerous regulatory aspects of eukaryotic cell biology, exists in the virulence factor proteins of bacterial pathogens. These O-linked phosphate modifications, unusual in prokaryotes, thus merit study for possible roles in pilus biogenesis and modulation of pilin chemistry for optimal in vivo function.
理解IV型菌毛的结构生物学，这种菌毛是众多细菌病原体毒力附着和运动的关键纤维，需要详细了解其组成菌毛蛋白亚基的三维结构和化学性质。淋病奈瑟菌菌毛蛋白针对分辨率为2.6埃的衍射数据进行X射线晶体学优化，并结合肽片段质谱分析，揭示了68位残基上的磷酸丝氨酸。磷酸丝氨酸在模拟的IV型菌毛表面，位于相邻菌毛蛋白分子的界面处暴露。将68位丝氨酸定点突变为丙氨酸表明，磷酸化的缺失改变了通过电子显微镜观察到的纤维形态，但对黏附、转化、菌毛形成或颤动运动没有显著影响。IV型菌毛蛋白亚基中蛋白质磷酸丝氨酸的结构和化学特征，有力地表明这种在真核细胞生物学众多调节方面起关键作用的修饰，存在于细菌病原体的毒力因子蛋白中。这些在原核生物中不常见的O-连接磷酸化修饰，因此值得研究其在菌毛生物合成中的可能作用以及对菌毛蛋白化学性质的调节，以实现最佳的体内功能。
