Novel Immunity Proteins Associated with Colicin M-like Bacteriocins Exhibit Promiscuous Protection in Pseudomonas.
Novel Immunity Proteins Associated with Colicin M-like Bacteriocins Exhibit Promiscuous Protection in Pseudomonas.
复制标题
与结菌素M样细菌蛋白相关的新型免疫蛋白在假单胞菌中表现出杂交的保护。
DOI：
10.3389/fmicb.2017.00093
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发表时间：
2017
影响因子：
5.2
通讯作者：
De Mot R
中科院分区：
文献类型：
--
作者：
Ghequire MG;Kemland L;De Mot R
与大肠杆菌素M相关的细菌素，通过裂解细胞壁前体脂质II起作用，已在γ-和β-变形菌中表征。根据物种的不同，免疫力由内膜锚定的周质蛋白或由整合的膜蛋白提供。然而，在假单胞菌中，大肠杆菌素M样细菌素的免疫伴侣仍然未知。基于假单胞菌基因组中的计算机分析，我们在这里确定了一个基因编码的推定的免疫合作伙伴，代表了一种新型的整合膜蛋白（PmiA，大肠杆菌素M样免疫A型）。通过在敏感菌株中异源表达pmiA基因，我们表明，大肠杆菌素M样细菌素的免疫力确实是由同源PmiA提供的。PmiA蛋白之间的序列同源性基本上是不存在的，除了一个保守的周质暴露的天冬氨酸残基的短基序。然而，PmiA的保护功能不会通过将该酸性残基改变为不带电荷的丙氨酸而被消除。PmiA的免疫性似乎是混杂的，以至于来自共享<40%成对氨基酸同一性的进化枝的PmiA同源物同样提供针对与原始PmiA连接的细菌素的保护。这项研究表明，多种免疫因子已经独立地进化到沉默脂质II靶向酶细菌素。它们宽松的细菌素免疫能力与屏蔽核酸酶细菌素酶结构域的免疫蛋白的严格特异性形成对比。在使用此类天然蛋白质抗生素或设计新型变体时，需要考虑相关免疫功能的性质。
Bacteriocins related to colicin M, acting via cleavage of the cell wall precursor lipid II, have been characterized in γ- and β-proteobacteria. Depending on the species, immunity is provided by either an inner membrane-anchored periplasmic protein or by an integral membrane protein. In Pseudomonas however, the immunity partner of colicin M-like bacteriocins remains unknown. Based on an in silico analysis in pseudomonad genomes, we here identify a gene encoding a putative immunity partner that represents a novel type of integral membrane protein (PmiA, Pseudomonas colicin M-like immunity type A). By heterologous expression of pmiA genes in susceptible strains, we show that immunity to colicin M-like bacteriocins is indeed provided by the cognate PmiA. Sequence homology among PmiA proteins is essentially absent, except for a short motif with a conserved periplasm-exposed aspartate residue. However, PmiA's protective function is not abolished by changing this acidic residue to the uncharged alanine. Immunity by PmiAs appears promiscuous to the extent that PmiA homologs from a clade sharing <40% pairwise amino acid identity, equally provide protection against the bacteriocin linked to the original PmiA. This study shows that multiple immunity factors have evolved independently to silence lipid II-targeting enzymatic bacteriocins. Their relaxed bacteriocin immunization capacity contrasts to the strict specificity of immunity proteins shielding the enzymatic domain of nuclease bacteriocins. The nature of associated immune functions needs consideration when using such natural protein antibiotics or designing novel variants.