Studholme David J, Pau Richard N
Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK.
BMC Microbiol. 2003 Dec 2;3:24. doi: 10.1186/1471-2180-3-24.
The transition metal molybdenum is essential for life. Escherichia coli imports this metal into the cell in the form of molybdate ions, which are taken up via an ABC transport system. In E. coli and other Proteobacteria molybdenum metabolism and homeostasis are regulated by the molybdate-responsive transcription factor ModE.
Orthologues of ModE are widespread amongst diverse prokaryotes, but not ubiquitous. We identified probable ModE-binding sites upstream of genes implicated in molybdenum metabolism in green sulphur bacteria and methanogenic Archaea as well as in Proteobacteria. We also present evidence of horizontal transfer of nitrogen fixation genes between green sulphur bacteria and methanogenic Archaea.
Whereas most of the archaeal helix-turn-helix-containing transcription factors belong to families that are Archaea-specific, ModE is unusual in that it is found in both Archaea and Bacteria. Moreover, its cognate upstream DNA recognition sequence is also conserved between Archaea and Bacteria, despite the fundamental differences in their core transcription machinery. ModE is the third example of a transcriptional regulator with a binding signal that is conserved in Bacteria and Archaea.
过渡金属钼对生命至关重要。大肠杆菌以钼酸根离子的形式将这种金属导入细胞，钼酸根离子通过一种ABC转运系统被摄取。在大肠杆菌和其他变形菌中，钼代谢和稳态由钼酸根响应转录因子ModE调控。
ModE的直系同源物在多种原核生物中广泛存在，但并非普遍存在。我们在绿硫细菌、产甲烷古菌以及变形菌中参与钼代谢的基因上游鉴定出了可能的ModE结合位点。我们还提供了绿硫细菌和产甲烷古菌之间固氮基因水平转移的证据。
虽然大多数含螺旋-转角-螺旋的古菌转录因子属于古菌特有的家族，但ModE不同寻常之处在于它同时存在于古菌和细菌中。此外，尽管古菌和细菌的核心转录机制存在根本差异，但其同源的上游DNA识别序列在古菌和细菌之间也是保守的。ModE是转录调节因子的第三个例子，其结合信号在细菌和古菌中是保守的。
