Twin-arginine translocation system in Helicobacter pylori: TatC, but not TatB, is essential for viability.
Twin-arginine translocation system in Helicobacter pylori: TatC, but not TatB, is essential for viability.
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DOI：
10.1128/mbio.01016-13
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发表时间：
2014-01-21
期刊：
影响因子：
6.4
通讯作者：
Maier RJ
中科院分区：
文献类型：
--
作者：
Benoit SL;Maier RJ
双精氨酸易位（达特）系统，需要运输折叠蛋白质穿过生物膜，尚未在胃病原体幽门螺杆菌的特点。迄今为止，对所有可用的幽门螺杆菌基因组序列的分析揭示了合成全功能达特系统所需的tatA、tatB和tatC的单拷贝的存在。基于在其信号序列中存在双精氨酸标志，只有四种幽门螺杆菌蛋白似乎是达特依赖性的：氢化酶（HydA）、过氧化氢酶相关蛋白（KapA）、生物素亚砜还原酶（BisC）和泛醇细胞色素氧化还原酶Rieske蛋白（FbcF）。在本研究中，靶向突变针对tatA、tatB、tatC或queA（下游基因控制）。虽然tatB和queA中的双同源重组突变很容易获得，但破坏tatA的尝试被证明是不成功的，而tatC的缺失导致单同源重组后的部分突变体，细胞保留了tatC的染色体拷贝。双同源重组tatC突变体只有在转化前引入质粒携带的异丙基-β-d-硫代半乳糖苷（IPTG）诱导的tatC拷贝时才能获得。这些条件tatC突变体只能在IPTG存在下生长，表明tatC在幽门螺杆菌中是必需的。tatB和tatC突变体具有较低的氢化酶和过氧化氢酶活性比野生型菌株没有，和tatC突变体的能力，以殖民小鼠胃相比，野生型受到严重影响。染色体互补的tatC突变体恢复氢化酶和过氧化氢酶活性的野生型水平，和额外的表达tatC在野生型细胞中导致Tat依赖性酶活性升高。出乎意料的是，达特菌株具有细胞包膜缺陷。这项工作首次报道了胃病原体幽门螺杆菌中双精氨酸移位（达特）系统的特征。虽然很容易获得tatB突变体，但只能产生单交换部分tatC突变体或条件性tatC突变体，表明tatC在幽门螺杆菌中是必需的，这是一个令人惊讶的发现，因为预测在该细菌中只有四种蛋白质被达特系统易位。氢化酶和过氧化氢酶的活性水平，预测的Tat依赖酶，在这些突变体的影响。此外，所有达特突变体显示细胞包膜缺陷，和tatC突变体在小鼠定植缺陷。
The twin-arginine translocation (Tat) system, needed to transport folded proteins across biological membranes, has not been characterized in the gastric pathogen Helicobacter pylori. Analysis of all H. pylori genome sequences available thus far reveals the presence of single copies of tatA, tatB, and tatC needed for the synthesis of a fully functional Tat system. Based on the presence of the twin-arginine hallmark in their signal sequence, only four H. pylori proteins appear to be Tat dependent: hydrogenase (HydA), catalase-associated protein (KapA), biotin sulfoxide reductase (BisC), and the ubiquinol cytochrome oxidoreductase Rieske protein (FbcF). In the present study, targeted mutations were aimed at tatA, tatB, tatC, or queA (downstream gene control). While double homologous recombination mutations in tatB and queA were easily obtained, attempts at disrupting tatA proved unsuccessful, while deletion of tatC led to partial mutants following single homologous recombination, with cells retaining a chromosomal copy of tatC. Double homologous recombination tatC mutants were obtained only when a plasmid-borne, isopropyl-β-d-thiogalactopyranoside (IPTG)-inducible copy of tatC was introduced prior to transformation. These conditional tatC mutants could grow only in the presence of IPTG, suggesting that tatC is essential in H. pylori. tatB and tatC mutants had lower hydrogenase and catalase activities than the wild-type strain did, and the ability of tatC mutants to colonize mouse stomachs was severely affected compared to the wild type. Chromosomal complementation of tatC mutants restored hydrogenase and catalase activities to wild-type levels, and additional expression of tatC in wild-type cells resulted in elevated Tat-dependent enzyme activities. Unexpectedly, the tat strains had cell envelope defects. This work reports the first characterization of the twin-arginine translocation (Tat) system in the gastric pathogen Helicobacter pylori. While tatB mutants were easily obtained, only single-crossover partial tatC mutants or conditional tatC mutants could be generated, indicating that tatC is essential in H. pylori, a surprising finding given the fact that only four proteins are predicted to be translocated by the Tat system in this bacterium. The levels of activity of hydrogenase and catalase, two of the predicted Tat-dependent enzymes, were affected in these mutants. In addition, all tat mutants displayed cell envelope defects, and tatC mutants were deficient in mouse colonization.