Identification of the genes involved in the secretion and self-immunity of lacticin Q, an unmodified leaderless bacteriocin from Lactococcus lactis QU 5
Identification of the genes involved in the secretion and self-immunity of lacticin Q, an unmodified leaderless bacteriocin from Lactococcus lactis QU 5
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DOI：
10.1099/mic.0.062943-0
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发表时间：
2012-12-01
期刊：
影响因子：
2.8
通讯作者：
Sonomoto, Kenji
中科院分区：
文献类型：
--
作者：
Iwatani, Shun;Yoneyama, Fuminori;Sonomoto, Kenji
乳酸乳酸乳球菌QU 5产生的乳糖素Q（LNQQ）是一种未修饰的线性细菌素，该线性细菌素是合成的，没有N末端铅肽。 LNQQ的体外合成和体内表达揭示了该无领导者肽的细胞内毒性，以及需要专用的分泌和生产者细胞的自我免疫系统的必要性。进一步的DNA测序和分析发现了在LNQQ基因座的基因上推定的11个。 ORF基因都没有与迄今为止表征的任何细菌素生物合成基因相似。然而，六个ORF基因（ORF2Q-7Q，不包括结构基因（LNQQ），在乳酸Z基因座（ORF2Z-7Z）上是高度保守的，该基因座（ORF2Z-7Z）是由L. lactis QU 14。ORF2Q（ORF2Z（ORF2Z）产生的LNQQ同源物。 ，其基因位于结构基因的上游，是一种推定的转录调节剂，而ORF6Q和ORF7Q（ORF6Z和ORF7Z）形成了Puthative ATP结合盒式转运蛋白。在异源宿主中，LNQQ和ORF3Q-7Q的膜蛋白质的蛋白质的表达允许LNQQ的细胞外产生。首先，通过两种方法，通过分泌活性的LNQQ肽，从而降低了细胞内毒性，其次是通过保护宿主细胞免受细胞外释放的LNQQ来介绍。细菌素，并提供了细菌分泌和免疫所需的生物合成基因的罕见例子。
Lacticin Q (LnqQ) produced by Lactococcus lactis QU 5 is an unmodified linear bacteriocin, which is synthesized without an N-terminal leader peptide. In vitro synthesis and in vivo expression of LnqQ have revealed the intracellular toxicity of this leaderless peptide, as well as the necessity of a dedicated secretion and self-immunity system of producer cells. Further DNA sequencing and analysis have discovered 11 putative on genes at the LnqQ locus. None of the orf genes showed similarities to any of the bacteriocin biosynthetic genes characterized to date; however, six orf genes (orf2q-7q, not including the structural gene (lnqQ), were highly conserved at the lacticin Z locus (orf2z-7z), which is a LnqQ homologue produced by L. lactis QU 14. ORF2q (ORF2z), the gene of which is located upstream of the structural gene, is a putative transcriptional regulator, whereas ORF6q and ORF7q (ORF6z and ORF7z) form a putative ATP-binding cassette transporter. The ORF3q-5q (ORF3z-5z) are all predicted to be membrane proteins with no clear functions. Co-expression of LnqQ and ORF3q-7q in a heterologous host allowed the extracellular production of LnqQ; additionally, the expression of ORF3q-7q rendered the host cells immune to LnqQ. This self-immunity was facilitated possibly by two means; firstly, by secreting the active LnqQ peptides, thus reducing the intracellular toxicity, and secondly, by protecting the host cells from extracellularly released LnqQ. This is the first report, to our knowledge, that describes intracellular toxicity of a leaderless bacteriocin and provides a rare example of biosynthetic genes that are required for bacteriocin secretion and immunity.