Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC, 27834, USA.
Department of Pathology and Laboratory Medicine, University of Texas Health Science Center, Houston, TX, 77030, USA.
Mol Microbiol. 2018 Nov;110(4):634-647. doi: 10.1111/mmi.14121. Epub 2018 Oct 15.
Spirochetes possess a unique periplasmic flagellar motor component called the collar. However, little is known about the composition or function of the flagellar collar proteins. To identify a collar protein, we have inactivated almost all genes annotated as motility-related in the Borrelia burgdorferi genome and identified only FlbB, which comprises the base of the collar. Since the major components of the collar complex remained unidentified, we took advantage of a protein-protein interaction map developed in another spirochete, Treponema pallidum to identify proteins of unknown function that could be collar proteins. Subsequently, using various comprehensive approaches, we identified a tetratricopeptide repeat protein BB0236 as a potential candidate for the collar. Biochemical assays indicated that FlbB interacts with BB0236. Furthermore, ∆bb0236 mutant analyses indicated that BB0236 is crucial for collar structure assembly, cellular morphology, motility, orientation of periplasmic flagella and assembly of other flagellar structures. Moreover, using comparative motor analyses, we propose how the collar structure is assembled in B. burgdorferi. Together, our studies provide new insights into the organization and the complex assembly inherent to the unique spirochetal collar structure.
螺旋体具有独特的周质鞭毛马达组件，称为环。然而，关于鞭毛环蛋白的组成或功能知之甚少。为了鉴定一种环蛋白，我们几乎灭活了博莱氏疏螺旋体基因组中注释为与运动相关的所有基因，仅鉴定出 FlbB，它构成了环的基部。由于环复合物的主要成分仍未被识别，我们利用另一种螺旋体苍白密螺旋体中开发的蛋白质-蛋白质相互作用图谱来鉴定可能是环蛋白的未知功能的蛋白质。随后，我们使用各种综合方法鉴定出一种四肽重复蛋白 BB0236 作为环的潜在候选蛋白。生化分析表明 FlbB 与 BB0236 相互作用。此外，∆bb0236 突变分析表明，BB0236 对于环结构组装、细胞形态、运动、周质鞭毛的取向以及其他鞭毛结构的组装至关重要。此外，我们通过比较运动分析，提出了博莱氏疏螺旋体中环结构的组装方式。总之，我们的研究为独特的螺旋体环结构的组织和复杂组装提供了新的见解。
