It takes two to tango: two TatA paralogues and two redox enzyme-specific chaperones are involved in the localization of twin-arginine translocase substrates in Campylobacter jejuni.
It takes two to tango: two TatA paralogues and two redox enzyme-specific chaperones are involved in the localization of twin-arginine translocase substrates in Campylobacter jejuni.
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DOI：
10.1099/mic.0.080713-0
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发表时间：
2014-09
期刊：
影响因子：
--
通讯作者：
Kelly DJ
中科院分区：
文献类型：
--
作者：
Liu YW;Hitchcock A;Salmon RC;Kelly DJ
食源性人畜共患病原体空肠弯曲杆菌具有复杂的电子传递链，这是在宿主体内生长所必需的，其中许多含有由双精氨酸转位酶（TAT）定位的辅助质周酶。本文报道了空肠C. NCTC 11168菌株TatA转位酶组分的两个同源序列，编码为cj1176c （tatA1）和cj0786 （tatA2）。在tatA1和tatA2基因中的一个或两个基因中构建的缺失突变体显示出不同的生长和酶活性表型。亚硫酸盐氧化酶（SorAB）、多铜氧化酶（CueO）和碱性磷酸酶（PhoX）完全依赖于TatA1来维持正确的质周活性。然而，硝酸盐还原酶（NapA）、甲酸脱氢酶（FdhA）和三甲胺n -氧化物还原酶（TorA）的活性在tatA2突变体中显著降低。相反，由富马酸甲基甲基醌还原酶（MfrA）的黄蛋白亚基催化的富马酸还原的特定速率在tatA1和tatA2突变体的质周部分是相似的，只有这两个基因的缺失才会破坏活性。然而，未加工的MfrA在tatA1（而不是tatA2）突变体的周质中积累，表明信号肽切割异常。令人惊讶的是，TatA2缺乏两个已知在大肠杆菌TatA中必不可少的保守残基（Gln8和Phe39），我们认为在没有TatA1的情况下它无法正常工作。最后，菌株NCTC 11168中只编码了两个TAT伴侣蛋白（FdhM和NapD），突变体研究证实它们分别对甲酸脱氢酶和硝酸还原酶组装具有高度特异性。因此，其他TAT底物在其生物发生过程中必须使用一般伴侣。
The food-borne zoonotic pathogen Campylobacter jejuni has complex electron transport chains required for growth in the host, many of which contain cofactored periplasmic enzymes localized by the twin-arginine translocase (TAT). We report here the identification of two paralogues of the TatA translocase component in C. jejuni strain NCTC 11168, encoded by cj1176c (tatA1) and cj0786 (tatA2). Deletion mutants constructed in either or both of the tatA1 and tatA2 genes displayed distinct growth and enzyme activity phenotypes. For sulphite oxidase (SorAB), the multi-copper oxidase (CueO) and alkaline phosphatase (PhoX), complete dependency on TatA1 for correct periplasmic activity was observed. However, the activities of nitrate reductase (NapA), formate dehydrogenase (FdhA) and trimethylamine N-oxide reductase (TorA) were significantly reduced in the tatA2 mutant. In contrast, the specific rate of fumarate reduction catalysed by the flavoprotein subunit of the methyl menaquinone fumarate reductase (MfrA) was similar in periplasmic fractions of both the tatA1 and the tatA2 mutants and only the deletion of both genes abolished activity. Nevertheless, unprocessed MfrA accumulated in the periplasm of the tatA1 (but not tatA2) mutant, indicating aberrant signal peptide cleavage. Surprisingly, TatA2 lacks two conserved residues (Gln8 and Phe39) known to be essential in Escherichia coli TatA and we suggest it is unable to function correctly in the absence of TatA1. Finally, only two TAT chaperones (FdhM and NapD) are encoded in strain NCTC 11168, which mutant studies confirmed are highly specific for formate dehydrogenase and nitrate reductase assembly, respectively. Thus, other TAT substrates must use general chaperones in their biogenesis.
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