The Crystal Structure of the Lipid II-degrading Bacteriocin Syringacin M Suggests Unexpected Evolutionary Relationships between Colicin M-like Bacteriocins
The Crystal Structure of the Lipid II-degrading Bacteriocin Syringacin M Suggests Unexpected Evolutionary Relationships between Colicin M-like Bacteriocins
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DOI：
10.1074/jbc.m112.400150
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发表时间：
2012-11-09
影响因子：
4.8
通讯作者：
Walker, Daniel
中科院分区：
文献类型：
--
作者：
Grinter, Rhys;Roszak, Aleksander W.;Walker, Daniel
类Colicin细菌素作为下一代抗生素具有潜在的临床和农业应用前景。这些潜在应用的关键是它们的高效性和物种特异性，使单一致病物种能够在对更广泛的微生物群落的干扰最小的情况下成为靶标。本文介绍了从丁香假单胞菌中分离到的类似粘菌素M的细菌素丁香素M的结构和功能。番茄DC3000。丁香素M通过针对脂质II的高度特异的磷酸酶活性杀死敏感细胞，最终抑制肽聚糖的合成。紫丁香素M和粘菌素M的结构比较表明，除了预期的同源C末端催化结构域之间的相似性外，这些蛋白的受体结合结构域具有惊人的结构相似性，它们没有明显的序列同源性。这表明，这些细菌素的新型受体结合和物种特异性的产生是由多样化的选择驱动的，而不是先前提出的多样化重组。此外，丁香素M的结构揭示了活性中心钙离子的存在，该离子由保守的天冬氨酸侧链配位，是催化活性所必需的。我们发现这个残基突变为丙氨酸会使丁香素M失活，并且突变蛋白的结构中没有金属离子。与活性部位存在的Ca~(2+)相一致，我们发现丁香素M的活性受Ca~(2+)、Mg~(2+)和Mn~(2+)的支持，并且在没有这些离子的情况下，该蛋白是催化失活的。
Colicin-like bacteriocins show potential as next generation antibiotics with clinical and agricultural applications. Key to these potential applications is their high potency and species specificity that enables a single pathogenic species to be targeted with minimal disturbance of the wider microbial community. Here we present the structure and function of the colicin M-like bacteriocin, syringacin M from Pseudomonas syringae pv. tomato DC3000. Syringacin M kills susceptible cells through a highly specific phosphatase activity that targets lipid II, ultimately inhibiting peptidoglycan synthesis. Comparison of the structures of syringacin M and colicin M reveals that, in addition to the expected similarity between the homologous C-terminal catalytic domains, the receptor binding domains of these proteins, which share no discernible sequence homology, share a striking structural similarity. This indicates that the generation of the novel receptor binding and species specificities of these bacteriocins has been driven by diversifying selection rather than diversifying recombination as suggested previously. Additionally, the structure of syringacin M reveals the presence of an active site calcium ion that is coordinated by a conserved aspartic acid side chain and is essential for catalytic activity. We show that mutation of this residue to alanine inactivates syringacin M and that the metal ion is absent from the structure of the mutant protein. Consistent with the presence of Ca2+ in the active site, we show that syringacin M activity is supported by Ca2+, along with Mg2+ and Mn2+, and the protein is catalytically inactive in the absence of these ions.