Role of individual nap gene cluster products in NapC-independent nitrate respiration of Wolinella succinogenes
Role of individual nap gene cluster products in NapC-independent nitrate respiration of Wolinella succinogenes
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DOI：
10.1099/mic.0.2007/009928-0
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发表时间：
2007-11-01
期刊：
影响因子：
2.8
通讯作者：
Simon, Jorg
中科院分区：
文献类型：
--
作者：
Kern, Melanie;Mager, Anke M.;Simon, Jorg
编码外质硝酸还原酶（NapA）的细菌nap基因簇是复杂多样的，而在大多数生物体中，向NapA提供电子的电子传递链的组成尚不清楚。异常,Wolinella succinogenes转移电子从甲酸甲基萘醌类池通过独立纳帕的膜结合c -型细胞色素NapC家庭。本文通过描述框架内基因失活突变体来评估W琥珀酸基因napAGHBFLD基因簇中单个orf的作用。试验了突变体在硝酸呼吸作用下的生长能力，测定了突变体的NapA含量和硝酸还原酶活性。napB和napD基因产物被证明是硝酸盐呼吸所必需的，napD是产生成熟的NapA所必需的。假定的膜结合甲基萘酚脱氢酶复合体NapGH的任何一个亚基失活几乎通过硝酸盐呼吸终止了生长。取代双精氨酸序列与缺失NapG具有相同的效果。缺乏NapF或NapL的突变体的表型表明，这两种蛋白都在NapA的组装和/或输出中起作用。这些数据证实了与napc无关的电子传递链的组成和NapA成熟的现有模型，并表明存在另一种电子传递途径。
Bacterial nap gene clusters, encoding periplasmic nitrate reductase (NapA), are complex and diverse, and the composition of the electron transport chain donating electrons to NapA is poorly characterized in most organisms. Exceptionally, Wolinella succinogenes transfers electrons from formate via the menaquinone pool to NapA independently of a membrane-bound c-type cytochrome of the NapC family. The role of individual ORFs of the W succinogenes napAGHBFLD gene cluster is assessed here by characterizing in-frame gene inactivation mutants. The ability of the mutants to grow by nitrate respiration was tested and their NapA content and specific nitrate reductase activity were determined. The napB and napD gene products proved to be essential for nitrate respiration, with NapD being required for the production of mature NapA. Inactivation of either subunit of the putative membrane-bound menaquinol dehydrogenase complex NapGH almost abolished growth by nitrate respiration. Substitution of the twin-arginine sequence of NapG had the same effect as absence of NapG. Phenotypes of mutants lacking either NapF or NapL suggest that both proteins function in NapA assembly and/or export. The data substantiate the current model of the composition of the NapC-independent electron transport chain as well as of NapA maturation, and indicate the presence of an alternative electron transport pathway to NapA.