Department of Chemistry, Umeå Centre for Microbial Research (UCMR), Umeå University, 90187, Umeå, Sweden.
Department of Odontology, Umeå University, 90187, Umeå, Sweden.
Commun Biol. 2021 Jan 25;4(1):106. doi: 10.1038/s42003-020-01621-w.
The Gram-negative bacterium Porphyromonas gingivalis is a secondary colonizer of the oral biofilm and is involved in the onset and progression of periodontitis. Its fimbriae, of type-V, are important for attachment to other microorganisms in the biofilm and for adhesion to host cells. The fimbriae are assembled from five proteins encoded by the mfa1 operon, of which Mfa5 is one of the ancillary tip proteins. Here we report the X-ray structure of the N-terminal half of Mfa5, which reveals a von Willebrand factor domain and two IgG-like domains. One of the IgG-like domains is stabilized by an intramolecular isopeptide bond, which is the first such bond observed in a Gram-negative bacterium. These features make Mfa5 structurally more related to streptococcal adhesins than to the other P. gingivalis Mfa proteins. The structure reported here indicates that horizontal gene transfer has occurred among the bacteria within the oral biofilm.
牙龈卟啉单胞菌是一种革兰氏阴性菌，是口腔生物膜的次要定植菌，与牙周炎的发生和发展有关。其菌毛属于 V 型，对于在生物膜中与其他微生物的附着以及与宿主细胞的黏附很重要。菌毛由 mfa1 操纵子编码的五个蛋白组装而成，其中 Mfa5 是辅助尖端蛋白之一。本研究报告了 Mfa5 的 N 端半结构域的 X 射线结构，揭示了一个血管性血友病因子结构域和两个 IgG 样结构域。其中一个 IgG 样结构域由一个分子内异肽键稳定，这是在革兰氏阴性菌中首次观察到的这种键。这些特征使 Mfa5 在结构上与链球菌黏附素更相关，而与其他牙龈卟啉单胞菌 Mfa 蛋白不同。本研究报告的结构表明，口腔生物膜内的细菌之间发生了水平基因转移。
