Ding Yan, Berezuk Alison, Khursigara Cezar M, Jarrell Ken F
Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
Microbiology (Reading). 2017 May;163(5):804-815. doi: 10.1099/mic.0.000464.
Archaella are the swimming organelles in the Archaea. Recently, the first archaellum regulator in the Euryarchaeota, EarA, was identified in , one of the model organisms used for archaellum studies. EarA binds to 6 bp consensus sequences upstream of the promoter to activate the transcription of the operon, which encodes most of the proteins required for archaella synthesis. In this study, synteny analysis showed that homologues are widely distributed in the phylum of Euryarchaeota, with the notable exception of extreme halophiles. We classified Euryarchaeota species containing homologues into five classes based on the genomic location of the genes relative to and chemotaxis operons. EarA homologues from , and successfully complemented the function of EarA in a mutant, demonstrated by the restoration of FlaB2 expression in Western blot analysis and the appearance of archaella on the cell surface in complemented cells. Furthermore, the 6 bp consensus sequence was also found in the promoter region in these methanogens, indicating that the EarA homologues ly use a similar mechanism to activate transcription of the operons in their own hosts. Attempts to demonstrate complementation of the function of EarA in a mutant by the EarA homologue of were unsuccessful, despite the presence of a copy of the 6 bp consensus EarA-binding sequence upstream of the promoter in the genome.
古菌鞭毛是古菌中的游动细胞器。最近，在嗜盐嗜碱古菌（古菌鞭毛研究中使用的模式生物之一）中鉴定出了广古菌门中的首个古菌鞭毛调节因子EarA。EarA与启动子上游的6个碱基对共有序列结合，以激活操纵子的转录，该操纵子编码古菌鞭毛合成所需的大部分蛋白质。在本研究中，共线性分析表明，EarA同源物广泛分布于广古菌门中，但极端嗜盐菌是明显的例外。我们根据EarA基因相对于fla和趋化性操纵子的基因组位置，将含有EarA同源物的广古菌物种分为五类。来自嗜盐嗜碱古菌、嗜热栖热菌和詹氏甲烷球菌的EarA同源物成功地补充了EarA在嗜盐嗜碱古菌突变体中的功能，这在蛋白质免疫印迹分析中FlaB2表达的恢复以及互补细胞中细胞表面出现古菌鞭毛得到了证明。此外，在这些产甲烷菌的fla启动子区域也发现了6个碱基对的共有序列，这表明EarA同源物可能在其自身宿主中使用类似的机制来激活fla操纵子的转录。尽管在嗜热栖热菌基因组的fla启动子上游存在一个6个碱基对的共有EarA结合序列拷贝，但试图通过嗜热栖热菌的EarA同源物来证明其在嗜盐嗜碱古菌突变体中对EarA功能的互补却未成功。
