Urbanowicz Anna, Lewandowski Dominik, Szpotkowski Kamil, Figlerowicz Marek
Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, 61-704, Poland.
Institute of Computing Science, University of Technology, Poznan, 60-965, Poland.
Sci Rep. 2016 Apr 26;6:25205. doi: 10.1038/srep25205.
The tick receptor for outer surface protein A (TROSPA) is the only identified factor involved in tick gut colonization by various Borrelia species. TROSPA is localized in the gut epithelium and can recognize and bind the outer surface bacterial protein OspA via an unknown mechanism. Based on earlier reports and our latest observations, we considered that TROSPA would be the first identified intrinsically disordered protein (IDP) involved in the interaction between a vector and a pathogenic microbe. To verify this hypothesis, we performed structural studies of a TROSPA mutant from Ixodes ricinus using both computational and experimental approaches. Irrespective of the method used, we observed that the secondary structure content of the TROSPA polypeptide chain is low. In addition, the collected SAXS data indicated that this protein is highly extended and exists in solution as a set of numerous conformers. These features are all commonly considered hallmarks of IDPs. Taking advantage of our SAXS data, we created structural models of TROSPA and proposed a putative mechanism for the TROSPA-OspA interaction. The disordered nature of TROSPA may explain the ability of a wide spectrum of Borrelia species to colonize the tick gut.
蜱虫外表面蛋白A受体（TROSPA）是唯一已确定的参与多种疏螺旋体属物种在蜱虫肠道定殖的因子。TROSPA定位于肠道上皮，可通过未知机制识别并结合细菌外表面蛋白OspA。基于早期报道和我们最新的观察结果，我们认为TROSPA将是首个被鉴定出的参与载体与致病微生物相互作用的内在无序蛋白（IDP）。为验证这一假设，我们使用计算和实验方法对蓖麻硬蜱的TROSPA突变体进行了结构研究。无论使用何种方法，我们都观察到TROSPA多肽链的二级结构含量较低。此外，收集到的小角X射线散射（SAXS）数据表明，该蛋白高度伸展，以一系列众多构象体的形式存在于溶液中。这些特征通常都被视为内在无序蛋白的标志。利用我们的SAXS数据，我们创建了TROSPA的结构模型，并提出了TROSPA与OspA相互作用的一种可能机制。TROSPA的无序性质可能解释了多种疏螺旋体属物种在蜱虫肠道定殖的能力。
