Lyme disease is an infection caused by the spirochete Borrelia burgdorferi after it is transmitted to a mammalian organism during a tick blood meal. B. burgdorferi encodes at least 140 lipoproteins located on the outer or inner membrane, thus facing the surroundings or the periplasmic space, respectively. However, most of the predicted lipoproteins are of unknown function, and only a few proteins are known to be essential for the persistence and virulence of the pathogen. One such protein is the periplasmic BB0323, which is indispensable for B. burgdorferi to cause Lyme disease and the function of which is associated with cell fission and outer membrane integrity. After expression and transport to the periplasm, BB0323 is cleaved into C‐terminal and N‐terminal domains by the periplasmic serine protease BB0104. The resulting N‐terminal domain is sufficient to ensure the survival of B. burgdorferi throughout the mouse–tick infection cycle. The crystal structure of the N‐terminal domain of BB0323 was determined at 2.35 Å resolution. The overall fold of the protein belongs to the spectrin superfamily, with the characteristic interconnected triple‐helical bundles known as spectrin repeats that function as linkers between different cell components in other organisms. Overall, the reported three‐dimensional structure of the N‐terminal domain of BB0323 not only reveals the molecular details of a protein that is essential for B. burgdorferi membrane integrity, cell fission and infectivity, but also suggests that spectrin repeats in bacteria are not limited to the EzrA proteins.

中文翻译：

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来自莱姆病病原体伯氏疏螺旋体的主要毒力因子BB0323 N末端结构域的晶体结构。

莱姆病是在a血餐期间传播给哺乳动物的螺旋体伯氏疏螺旋体引起的感染。B. burgdorferi编码位于外膜或内膜上的至少140种脂蛋白，分别面对周围环境或周质空间。但是，大多数预测的脂蛋白功能未知，只有少数几种蛋白对病原体的持久性和毒力至关重要。一种这样的蛋白是周质BB0323，它对于B. burgdorferi必不可少引起莱姆病，其功能与细胞分裂和外膜完整性有关。表达并运输到周质后，BB0323被周质丝氨酸蛋白酶BB0104切割成C端和N端结构域。产生的N末端结构域足以确保B. burgdorferi的生存在整个鼠标滴答感染周期中。BB0323 N末端结构域的晶体结构是在2.35Å分辨率下测定的。蛋白质的整体折叠属于血影蛋白超家族，具有相互关联的特征性三螺旋束，称为血影蛋白重复序列​​，可充当其他生物中不同细胞成分之间的接头。总体而言，所报道的BB0323 N末端结构域的三维结构不仅揭示了对B. burgdorferi膜完整性，细胞分裂和感染性必不可少的蛋白质的分子细节，而且还表明细菌中的血影蛋白重复不是仅限于EzrA蛋白。