As part of the Virus-X Consortium that aims to identify and characterize novel proteins and enzymes from bacteriophages and archaeal viruses, the genes of the putative lytic proteins XepA from Bacillus subtilis prophage PBSX and YomS from prophage SPβ were cloned and the proteins were subsequently produced and functionally characterized. In order to elucidate the role and the molecular mechanism of XepA and YomS, the crystal structures of these proteins were solved at resolutions of 1.9 and 1.3 Å, respectively. XepA consists of two antiparallel β-sandwich domains connected by a 30-amino-acid linker region. A pentamer of this protein adopts a unique dumbbell-shaped architecture consisting of two discs and a central tunnel. YomS (12.9 kDa per monomer), which is less than half the size of XepA (30.3 kDa), shows homology to the C-terminal part of XepA and exhibits a similar pentameric disc arrangement. Each β-sandwich entity resembles the fold of typical cytoplasmic membrane-binding C2 domains. Only XepA exhibits distinct cytotoxic activity in vivo, suggesting that the N-terminal pentameric domain is essential for this biological activity. The biological and structural data presented here suggest that XepA disrupts the proton motive force of the cytoplasmatic membrane, thus supporting cell lysis.

中文翻译：

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枯草芽孢杆菌前噬菌体裂解盒蛋白 XepA 和 YomS 的晶体结构。


Virus-X 联盟旨在识别和表征来自噬菌体和古细菌病毒的新型蛋白质和酶，作为该联盟的一部分，克隆了来自枯草芽孢杆菌原噬菌体 PBSX 的假定裂解蛋白 XepA 和来自原噬菌体 SPβ 的 YomS 的基因，并随后生产了这些蛋白质并具有功能特征。为了阐明 XepA 和 YomS 的作用和分子机制，分别以 1.9 和 1.3 Å 的分辨率解析了这些蛋白质的晶体结构。 XepA 由两个反向平行的 β-夹心结构域组成，通过 30 个氨基酸的接头区域连接。这种蛋白质的五聚体采用独特的哑铃形结构，由两个圆盘和一个中央隧道组成。 YomS（每个单体 12.9 kDa）小于 XepA（30.3 kDa）大小的一半，与 XepA 的 C 端部分具有同源性，并表现出类似的五聚体盘排列。每个 β-夹心实体类似于典型的细胞质膜结合 C2 结构域的折叠。只有 XepA 在体内表现出独特的细胞毒活性，表明 N 端五聚结构域对于这种生物活性至关重要。这里提供的生物学和结构数据表明 XepA 破坏细胞质膜的质子动力，从而支持细胞裂解。