Dowdell Alexander S, Murphy Maxwell D, Azodi Christina, Swanson Selene K, Florens Laurence, Chen Shiyong, Zückert Wolfram R
Department of Microbiology, Molecular Genetics & Immunology, University of Kansas School of Medicine, Kansas City, Kansas, USA.
Proteomics Center, Stowers Institute for Medical Research, Kansas City, Missouri, USA.
J Bacteriol. 2017 Feb 28;199(6). doi: 10.1128/JB.00658-16. Print 2017 Mar 15.
The Lyme disease spirochete is unique among bacteria in its large number of lipoproteins that are encoded by a small, exceptionally fragmented, and predominantly linear genome. Peripherally anchored in either the inner or outer membrane and facing either the periplasm or the external environment, these lipoproteins assume varied roles. A prominent subset of lipoproteins functioning as the apparent linchpins of the enzootic tick-vertebrate infection cycle have been explored as vaccine targets. Yet, most of the lipoproteome has remained uncharacterized. Here, we comprehensively and conclusively localize the lipoproteome by applying established protein localization assays to a newly generated epitope-tagged lipoprotein expression library and by validating the obtained individual protein localization results using a sensitive global mass spectrometry approach. The derived consensus localization data indicate that 86 of the 125 analyzed lipoproteins encoded by are secreted to the bacterial surface. Thirty-one of the remaining 39 periplasmic lipoproteins are retained in the inner membrane, with only 8 lipoproteins being anchored in the periplasmic leaflet of the outer membrane. The localization of 10 lipoproteins was further defined or revised, and 52 surface and 23 periplasmic lipoproteins were newly localized. Cross-referencing prior studies revealed that the borrelial surface lipoproteome contributing to the host-pathogen interface is encoded predominantly by plasmids. Conversely, periplasmic lipoproteins are encoded mainly by chromosomal loci. These studies close a gap in our understanding of the functional lipoproteome of an important human pathogen and set the stage for more in-depth studies of thus-far-neglected spirochetal lipoproteins. The small and exceptionally fragmented genome of the Lyme disease spirochete encodes over 120 lipoproteins. Studies in the field have predominantly focused on a relatively small number of surface lipoproteins that play important roles in the transmission and pathogenesis of this global human pathogen. Yet, a comprehensive spatial assessment of the entire borrelial lipoproteome has been missing. The current study newly identifies 52 surface and 23 periplasmic lipoproteins. Overall, two-thirds of the lipoproteins localize to the surface, while outer membrane lipoproteins facing the periplasm are rare. This analysis underscores the dominant contribution of lipoproteins to the spirochete's rather complex and adaptable host-pathogen interface, and it encourages further functional exploration of its lipoproteome.
莱姆病螺旋体在细菌中独具特色，其大量脂蛋白由一个小的、异常碎片化且主要为线性的基因组编码。这些脂蛋白外周锚定在内膜或外膜上，面向周质或外部环境，发挥着多种作用。作为动物蜱 - 脊椎动物感染循环中明显关键环节的一类重要脂蛋白已被探索作为疫苗靶点。然而，大多数脂蛋白组仍未得到表征。在此，我们通过将已建立的蛋白质定位分析方法应用于新生成的带有表位标签的脂蛋白表达文库，并使用灵敏的全局质谱方法验证所获得的单个蛋白质定位结果，全面且确凿地定位了脂蛋白组。得出的共识定位数据表明，在分析的由[具体基因名称]编码的125种脂蛋白中，有86种分泌到细菌表面。其余39种周质脂蛋白中有31种保留在内膜中，只有8种脂蛋白锚定在外膜的周质小叶中。10种脂蛋白的定位得到了进一步明确或修正，52种表面脂蛋白和23种周质脂蛋白被新定位。交叉引用先前的研究发现，构成宿主 - 病原体界面的疏螺旋体表面脂蛋白组主要由质粒编码。相反，周质脂蛋白主要由染色体基因座编码。这些研究填补了我们对一种重要人类病原体功能性脂蛋白组理解上的空白，并为进一步深入研究迄今被忽视的螺旋体脂蛋白奠定了基础。莱姆病螺旋体小且异常碎片化的基因组编码超过120种脂蛋白。该领域的研究主要集中在相对少数在这种全球人类病原体的传播和发病机制中起重要作用的表面脂蛋白上。然而，对整个疏螺旋体脂蛋白组的全面空间评估一直缺失。当前研究新鉴定出52种表面脂蛋白和23种周质脂蛋白。总体而言，三分之二的[具体名称]脂蛋白定位于表面，而面向周质的外膜脂蛋白很少见。这一分析强调了脂蛋白对螺旋体相当复杂且适应性强的宿主 - 病原体界面的主要贡献，并鼓励对其脂蛋白组进行进一步的功能探索。
