Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, 35233, USA.
Department of Oral Rehabilitation & Biosciences, Oregon Health & Science University, Portland, OR, 97239, USA.
Nat Commun. 2024 Nov 3;15(1):9500. doi: 10.1038/s41467-024-53923-w.
Supercoiled flagellar filaments function as mechanical propellers within the bacterial flagellum complex, playing a crucial role in motility. Flagellin, the building block of the filament, features a conserved inner D0/D1 core domain across different bacterial species. In contrast, approximately half of the flagellins possess additional, highly divergent outer domain(s), suggesting varied functional potential. In this study, we report atomic structures of flagellar filaments from three distinct bacterial species: Cupriavidus gilardii, Stenotrophomonas maltophilia, and Geovibrio thiophilus. Our findings reveal that the flagella from the facultative anaerobic G. thiophilus possesses a significantly more negatively charged surface, potentially enabling adhesion to positively charged minerals. Furthermore, we analyze all AlphaFold predicted structures for annotated bacterial flagellins, categorizing the flagellin outer domains into 682 structural clusters. This classification provides insights into the prevalence and experimental verification of these outer domains. Remarkably, two of the flagellar structures reported herein belong to a distinct cluster, indicating additional opportunities on the study of the functional diversity of flagellar outer domains. Our findings underscore the complexity of bacterial flagellins and open up possibilities for future studies into their varied roles beyond motility.
超螺旋鞭毛丝在细菌鞭毛复合物中充当机械推进器，在运动中起着关键作用。鞭毛蛋白是丝的构建块，在不同的细菌物种中具有保守的内部 D0/D1 核心结构域。相比之下，大约一半的鞭毛蛋白具有额外的、高度分化的外部结构域，表明具有不同的功能潜力。在这项研究中，我们报告了三种不同细菌的鞭毛丝的原子结构：铜绿假单胞菌、嗜麦芽寡养单胞菌和硫杆菌属。我们的发现表明，兼性厌氧的 G. thiophilus 的鞭毛具有显著更负的表面电荷，可能能够黏附带正电荷的矿物质。此外，我们分析了所有已注释的细菌鞭毛蛋白的 AlphaFold 预测结构，将鞭毛蛋白的外部结构域分为 682 个结构簇。这种分类为研究这些外部结构域的普遍性和实验验证提供了思路。值得注意的是，本文报告的两个鞭毛结构属于一个独特的簇，这表明在研究鞭毛外部结构域的功能多样性方面还有更多的机会。我们的发现强调了细菌鞭毛蛋白的复杂性，并为进一步研究它们在运动以外的多种作用开辟了可能性。
