Department of Molecular Systems Biology, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, 04318 Leipzig, Germany.
Department of Applied and Ecological Microbiology, Institute of Microbiology, Friedrich Schiller University, Philosophenweg 12, 07743 Jena, Germany.
J Proteomics. 2018 Jun 15;181:36-46. doi: 10.1016/j.jprot.2018.03.030. Epub 2018 Apr 1.
Organohalide respiration (OHR), comprising the reductive dehalogenation of halogenated organic compounds, is subject to a unique memory effect and long-term transcriptional downregulation of the involved genes in Sulfurospirillum multivorans. Gene expression ceases slowly over approximately 100 generations in the absence of tetrachloroethene (PCE). However, the molecular mechanisms of this regulation process are not understood. We show here that Sulfurospirillum halorespirans undergoes the same type of regulation when cultivated without chlorinated ethenes for a long period of time. In addition, we compared the proteomes of S. halorespirans cells cultivated in the presence of PCE with those of cells long- and short-term cultivated with nitrate as the sole electron acceptor. Important OHR-related proteins previously unidentified in S. multivorans include a histidine kinase, a putative quinol dehydrogenase membrane protein, and a PCE-induced porin. Since for some regulatory proteins a posttranslational regulation of activity by lysine acetylations is known, we also analyzed the acetylome of S. halorespirans, revealing that 32% of the proteome was acetylated in at least one condition. The data indicate that the response regulator and the histidine kinase of a two-component system most probably involved in induction of PCE respiration are highly acetylated during short-term cultivation with nitrate in the absence of PCE.
The so far unique long-term downregulation of organohalide respiration is now identified in a second species suggesting a broader distribution of this regulatory phenomenon. An improved protein extraction method allowed the identification of proteins most probably involved in transcriptional regulation of OHR in Sulfurospirillum spp. Our data indicate that acetylations of regulatory proteins are involved in this extreme, sustained standby-mode of metabolic enzymes in the absence of a substrate. This first published acetylome of Epsilonproteobacteria might help to study other ecologically or medically important species of this clade.
有机卤化物呼吸（OHR）包括卤代有机化合物的还原脱卤，受独特的记忆效应和 Sulfurospirillum multivorans 中涉及基因的长期转录下调的影响。在没有四氯乙烯（PCE）的情况下，基因表达大约在 100 代后缓慢停止。然而，这种调节过程的分子机制尚不清楚。我们在这里表明，当长时间不培养氯化乙稀时，Sulfurospirillum halorespirans 也会经历相同类型的调节。此外，我们比较了在存在 PCE 时培养的 S. halorespirans 细胞的蛋白质组与长期和短期以硝酸盐作为唯一电子受体培养的细胞的蛋白质组。在 S. multivorans 中以前未鉴定的重要 OHR 相关蛋白包括组氨酸激酶、一种假定的醌脱氢酶膜蛋白和 PCE 诱导的孔蛋白。由于一些调节蛋白的活性通过赖氨酸乙酰化进行翻译后调节，我们还分析了 S. halorespirans 的乙酰组，结果表明在至少一种条件下，32%的蛋白质组被乙酰化。数据表明，在没有 PCE 的情况下，短时间内以硝酸盐作为唯一电子受体培养时，参与诱导 PCE 呼吸的双组分系统的反应调节子和组氨酸激酶高度乙酰化。
目前在第二个物种中发现了有机卤化物呼吸的独特长期下调，这表明这种调节现象的分布更为广泛。一种改进的蛋白质提取方法鉴定了 Sulfurospirillum spp 中 OHR 转录调节中最有可能涉及的蛋白质。我们的数据表明，调节蛋白的乙酰化参与了在没有底物的情况下代谢酶的这种极端持续备用模式。这是首次发表的 Epsilonproteobacteria 的乙酰组可能有助于研究该分支中其他具有生态或医学重要性的物种。
