Gene Cluster Responsible for Secretion of and Immunity to Multiple Bacteriocins, the NKR-5-3 Enterocins
Gene Cluster Responsible for Secretion of and Immunity to Multiple Bacteriocins, the NKR-5-3 Enterocins
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DOI：
10.1128/aem.02312-14
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发表时间：
2014-11-01
影响因子：
4.4
通讯作者：
Sonomoto, Kenji
中科院分区：
文献类型：
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作者：
Ishibashi, Naoki;Himeno, Kohei;Sonomoto, Kenji
从泰国发酵鱼中分离到的粪肠球菌NKR-5-3具有产生5种细菌素的独特能力，即肠毒素NKR-5-3A、-B、-C、-D和-Z(Ent53A、Ent53B、Ent53C、Ent53D和Ent53Z)。基因组文库的遗传分析表明，编码这些多肽(Ent53B除外)的细菌素结构基因(EnkA[ent53A]、enkC[ent53C]、enkD[ent53D]和enkZ[ent53Z])位于彼此附近。这个NKR-5-3ACDZ(Ent53ACDZ)肠球蛋白基因簇(约13kb)包括一些细菌素生物合成基因，如ABC转运蛋白基因(EnkT)、两个免疫基因(enkIaz和enkIc)、一个反应调节基因(EnkR)和一个组氨酸蛋白激酶(EnkK)。对enkT和Delta enkT突变株的异源表达研究表明，enkT负责Ent53A、Ent53C、Ent53D和Ent53Z的分泌，这表明EnkT是一种广泛的ABC转运蛋白，有助于这些细菌素的有效生产。此外，还发现EnkIaz和EnkIc能赋予相应细菌素自身免疫力。此外，对Delta enkRK突变株的细菌素诱导分析表明，EnkR和EnkK是细菌素产生的调控蛋白，它们与Ent53D一起构成了一个三组分的调控系统。因此，Ent53ACDZ基因簇对于NKR-5-3肠毒素的生物合成和调控是必不可少的，据我们所知，这是第一个证明ABC转运蛋白分泌多种细菌素的报道。
Enterococcus faecium NKR-5-3, isolated from Thai fermented fish, is characterized by the unique ability to produce five bacteriocins, namely, enterocins NKR-5-3A, -B, -C, -D, and -Z (Ent53A, Ent53B, Ent53C, Ent53D, and Ent53Z). Genetic analysis with a genome library revealed that the bacteriocin structural genes (enkA [ent53A], enkC [ent53C], enkD [ent53D], and enkZ [ent53Z]) that encode these peptides (except for Ent53B) are located in close proximity to each other. This NKR-5-3ACDZ (Ent53ACDZ) enterocin gene cluster (approximately 13 kb long) includes certain bacteriocin biosynthetic genes such as an ABC transporter gene (enkT), two immunity genes (enkIaz and enkIc), a response regulator (enkR), and a histidine protein kinase (enkK). Heterologous-expression studies of enkT and Delta enkT mutant strains showed that enkT is responsible for the secretion of Ent53A, Ent53C, Ent53D, and Ent53Z, suggesting that EnkT is a wide-range ABC transporter that contributes to the effective production of these bacteriocins. In addition, EnkIaz and EnkIc were found to confer self-immunity to the respective bacteriocins. Furthermore, bacteriocin induction assays performed with the Delta enkRK mutant strain showed that EnkR and EnkK are regulatory proteins responsible for bacteriocin production and that, together with Ent53D, they constitute a three-component regulatory system. Thus, the Ent53ACDZ gene cluster is essential for the biosynthesis and regulation of NKR-5-3 enterocins, and this is, to our knowledge, the first report that demonstrates the secretion of multiple bacteriocins by an ABC transporter.