Department of Molecular Biology, Umeå University, Umeå SE-90187, Sweden.
Laboratory for Molecular Infection Medicine Sweden, Umeå University, Umeå SE-90187, Sweden.
Proc Natl Acad Sci U S A. 2021 Nov 23;118(47). doi: 10.1073/pnas.2111418118.
The protein MakA was discovered as a motility-associated secreted toxin from Here, we show that MakA is part of a gene cluster encoding four additional proteins: MakB, MakC, MakD, and MakE. MakA, MakB, and MakE were readily detected in culture supernatants of wild-type , whereas secretion was very much reduced from a flagellum-deficient mutant. Crystal structures of MakA, MakB, and MakE revealed a structural relationship to a superfamily of bacterial pore-forming toxins. Expression of MakA/B/E in resulted in toxicity toward used as a predatory model organism. None of these Mak proteins alone or in pairwise combinations were cytolytic, but an equimolar mixture of MakA, MakB, and MakE acted as a tripartite cytolytic toxin in vitro, causing lysis of erythrocytes and cytotoxicity on cultured human colon carcinoma cells. Formation of oligomeric complexes on liposomes was observed by electron microscopy. Oligomer interaction with membranes was initiated by MakA membrane binding followed by MakB and MakE joining the assembly of a pore structure. A predicted membrane insertion domain of MakA was shown by site-directed mutagenesis to be essential for toxicity toward Bioinformatic analyses revealed that the gene cluster is present as a genomic island in the vast majority of sequenced genomes of and the fish pathogen We suggest that the hitherto-unrecognized cytolytic MakA/B/E toxin can contribute to Vibrionaceae fitness and virulence potential in different host environments and organisms.
该蛋白 MakA 是一种运动相关的分泌性毒素，最初在 中发现。在这里，我们表明 MakA 是编码四个额外蛋白的基因簇的一部分：MakB、MakC、MakD 和 MakE。在野生型的培养上清液中，很容易检测到 MakA、MakB 和 MakE，而从鞭毛缺陷突变体中分泌的量则大大减少。MakA、MakB 和 MakE 的晶体结构揭示了与细菌孔形成毒素超家族的结构关系。在 中表达 MakA/B/E 导致了作为捕食模型生物的 细胞毒性。单独的这些 Mak 蛋白或两两组合都没有细胞毒性，但 MakA、MakB 和 MakE 的等摩尔混合物在体外表现出作为三分体细胞毒性毒素的作用，导致红细胞溶解和培养的人结肠癌细胞的细胞毒性。通过电子显微镜观察到脂质体上形成的寡聚复合物。通过 MakA 与膜的结合启动了寡聚体与膜的相互作用，随后 MakB 和 MakE 加入孔结构的组装。通过定点突变显示 MakA 的预测膜插入结构域对于对 的毒性是必需的。生物信息学分析表明，该基因簇作为基因组岛存在于绝大多数测序的 属和鱼类病原体 属的基因组中。我们认为，迄今未被识别的细胞毒性 MakA/B/E 毒素可以在不同的宿主环境和生物中有助于弧菌科的适应性和毒力潜力。
