海洋甲烷球菌利用含硒代半胱氨酸(Sec-)的蛋白质(硒蛋白),主要活跃于生物体的初级能量代谢,产甲烷。在硒耗尽期间,M.maripaludis使用一组含有半胱氨酸(Cys)的酶代替Sec。编码这些含Sec-/Cys同种型的基因是唯一已知的表达受细胞硒状态影响的基因。使用蛋白质组学和转录组学,大约。7%和12%,分别,发现所有基因/蛋白质的差异表达/合成响应于硒供应。一些确定的基因涉及甲烷生成,固氮酶功能,和推定的运输者。硒消耗下推定转运蛋白的转录物丰度增加表明该生物努力利用硒的替代来源。已知M.maripaludis利用亚硒酸盐和二甲基硒化物作为硒源。要扩展此列表,对硒敏感的报告菌株与其他9种进行了评估,与环境相关的硒物种。虽然有些效果与亚硒酸盐非常相似,其他在较低浓度下有效利用。相反,硒酸盐和硒代氨基酸仅在非生理高浓度下使用,根本没有使用两种化合物。为了解决硒调节的推定转运蛋白的作用,测试了缺乏一种或两种推定的转运蛋白的M.maripaludis突变菌株利用不同硒物种的能力。在通过功能丧失诱变分析的五种推定的转运蛋白中,似乎没有绝对需要使用任何测试的硒物种,表明它们具有冗余和/或重叠的特异性,或者不是专用的硒转运蛋白。
目的:虽然过去已经对微生物中的硒代谢进行了深入研究,到目前为止,尚未采用全局基因表达方法。此外,使用不同的硒源,通过生物和非生物过程可以在环境上广泛互换,以前也没有广泛研究过。海洋甲烷球菌JJ非常适合这种分析,由于其已知的硒的使用和可用的遗传工具。因此,通过转录组学和蛋白质组学分析获得了关于马马氏藻硒调节子的总体观点,这激发了进一步的实验。这证明了硒源M.maripaludis的使用以前是未知的。此外,尽管到目前为止没有成功,但有人试图查明潜在的硒转运蛋白基因,以加深我们对这种重要模式生物中微量元素利用的理解。
Methanococcus maripaludis utilizes selenocysteine- (Sec-) containing proteins (
selenoproteins), mostly active in the organism\'s primary energy metabolism, methanogenesis. During selenium depletion, M. maripaludis employs a set of enzymes containing cysteine (Cys) instead of Sec. The genes coding for these Sec-/Cys-containing isoforms were the only genes known of which expression is influenced by the selenium status of the cell. Using proteomics and transcriptomics, approx. 7% and 12%, respectively, of all genes/proteins were found differentially expressed/synthesized in response to the selenium supply. Some of the genes identified involve methanogenesis, nitrogenase functions, and putative transporters. An increase of transcript abundance for putative transporters under selenium depletion indicated the organism\'s effort to tap into alternative sources of selenium. M. maripaludis is known to utilize selenite and dimethylselenide as selenium sources. To expand this list, a selenium-responsive reporter strain was assessed with nine other, environmentally relevant selenium species. While the effect of some was very similar to that of selenite, others were effectively utilized at lower concentrations. Conversely, selenate and seleno-amino acids were only utilized at unphysiologically high concentrations and two compounds were not utilized at all. To address the role of the selenium-regulated putative transporters, M. maripaludis mutant strains lacking one or two of the putative transporters were tested for the capability to utilize the different selenium species. Of the five putative transporters analyzed by loss-of-function mutagenesis, none appeared to be absolutely required for utilizing any of the selenium species tested, indicating they have redundant and/or overlapping specificities or are not dedicated selenium transporters.
OBJECTIVE: While selenium metabolism in microorganisms has been studied intensively in the past, global gene expression approaches have not been employed so far. Furthermore, the use of different selenium sources, widely environmentally interconvertible via biotic and abiotic processes, was also not extensively studied before. Methanococcus maripaludis JJ is ideally suited for such analyses, thanks to its known selenium usage and available genetic tools. Thus, an overall view on the selenium regulon of M. maripaludis was obtained via transcriptomic and proteomic analyses, which inspired further experimentation. This led to demonstrating the use of selenium sources M. maripaludis was previously not known to employ. Also, an attempt-although so far unsuccessful-was made to pinpoint potential selenium transporter genes, in order to deepen our understanding of trace element utilization in this important model organism.