Identification of a Novel N-Acetylmuramic Acid Transporter in Tannerella forsythia
Identification of a Novel N-Acetylmuramic Acid Transporter in Tannerella forsythia
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DOI：
10.1128/jb.00473-16
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发表时间：
2016-11-01
影响因子：
3.2
通讯作者：
Sharma, Ashu
中科院分区：
文献类型：
--
作者：
Ruscitto, Angela;Hottmann, Isabel;Sharma, Ashu
Tannerella pasthia是一种革兰氏阴性牙周病原体，缺乏从头合成氨基糖N-乙酰胞壁酸（MurNAc）和N-乙酰葡糖胺（GlcNAc）的能力，这些氨基糖形成肽聚糖骨架的二糖重复单元。T.西印度群岛依赖于从环境中吸收这些糖，这是迄今为止尚未开发的。在这里，我们确定了一个新的T.参与MurNAc跨内膜的摄取的大肠杆菌MurQ醚酶的同源物，其特征在于参与MurNAc-6-磷酸（MurNAc-6-P）转化为GlcNAc-6-P。编码这些组分的基因被鉴定为位于推定的肽聚糖回收位点下游的跨越Tanf_08375至Tanf_08385的三基因簇。我们发现，三个基因，Tanf_08375，Tanf_08380，和Tanf_08385，分别编码一个MurNAc转运蛋白，一个假定的糖激酶，和MurQ醚酶，转录连接。Tanf_08375和Tanf_08380基因一起反式互补，而不是单独互补，挽救了E.在磷酸转移酶（PTS）系统依赖性MurNAc转运蛋白MurP中缺陷的大肠杆菌突变体以及在MurP和PTS系统的组分中缺陷的双重突变体的突变体在MurNAc上生长。此外，在E.大肠杆菌引起培养基中MurNAc的耗尽，进一步证实了这一观察结果。我们的研究结果表明，Tanf_08375和Tanf_08380的产物构成了一种新的非PTS MurNAc转运蛋白系统，该系统似乎广泛存在于拟杆菌门的细菌中。据我们所知，这是第一次鉴定的PTS-独立的MurNAc转运蛋白在bacteri.IMPORTANCEIn这项研究中，我们报告了一种新的转运蛋白肽聚糖氨基糖N-乙酰胞壁酸（MurNAc）在牙周病原体T。艾西娅自20世纪80年代末以来，T.西印度群岛是一种MurNAc营养缺陷型，依赖于这种必需糖的环境来源。大多数糖转运蛋白，特别是MurNAc转运蛋白MurP，需要PTS磷酸化来驱动糖的摄取和同时磷酸化通过革兰氏阴性细菌的内膜。我们的研究发现了一种新型的不依赖PTS的MurNAc转运蛋白，尽管到目前为止，它似乎是T.在口腔和肠道的一系列细菌中，特别是拟杆菌门的细菌中可能存在。
Tannerella forsythia is a Gram-negative periodontal pathogen lacking the ability to undergo de novo synthesis of amino sugars N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) that form the disaccharide repeating unit of the peptidoglycan backbone. T. forsythia relies on the uptake of these sugars from the environment, which is so far unexplored. Here, we identified a novel transporter system of T. forsythia involved in the uptake of MurNAc across the inner membrane and characterized a homolog of the Escherichia coli MurQ etherase involved in the conversion of MurNAc-6-phosphate (MurNAc-6-P) to GlcNAc-6-P. The genes encoding these components were identified on a three-gene cluster spanning Tanf_08375 to Tanf_08385 located downstream from a putative peptidoglycan recycling locus. We show that the three genes, Tanf_08375, Tanf_08380, and Tanf_08385, encoding a MurNAc transporter, a putative sugar kinase, and a MurQ etherase, respectively, are transcriptionally linked. Complementation of the Tanf_08375 and Tanf_08380 genes together in trans, but not individually, rescued the inability of an E. coli mutant deficient in the phosphotransferase (PTS) system-dependent MurNAc transporter MurP as well as that of a double mutant deficient in MurP and components of the PTS system to grow on MurNAc. In addition, complementation with this two-gene construct in E. coli caused depletion of MurNAc in the medium, further confirming this observation. Our results show that the products of Tanf_08375 and Tanf_08380 constitute a novel non-PTS MurNAc transporter system that seems to be widespread among bacteria of the Bacteroidetes phylum. To the best of our knowledge, this is the first identification of a PTS-independent MurNAc transporter in bacteria.IMPORTANCEIn this study, we report the identification of a novel transporter for peptidoglycan amino sugar N-acetylmuramic acid (MurNAc) in the periodontal pathogen T. forsythia. It has been known since the late 1980s that T. forsythia is a MurNAc auxotroph relying on environmental sources for this essential sugar. Most sugar transporters, and the MurNAc transporter MurP in particular, require a PTS phosphorelay to drive the uptake and concurrent phosphorylation of the sugar through the inner membrane in Gram-negative bacteria. Our study uncovered a novel type of PTS-independent MurNAc transporter, and although so far, it seems to be unique to T. forsythia, it may be present in a range of bacteria both of the oral cavity and gut, especially of the phylum Bacteroidetes.