van Vliet Arnoud H M, Poppelaars Sophie W, Davies Beverly J, Stoof Jeroen, Bereswill Stefan, Kist Manfred, Penn Charles W, Kuipers Ernst J, Kusters Johannes G
Department of Gastroenterology and Hepatology, Erasmus Medical Center, Rotterdam, The Netherlands.
Infect Immun. 2002 Jun;70(6):2846-52. doi: 10.1128/IAI.70.6.2846-2852.2002.
The important human pathogen Helicobacter pylori requires the abundant expression and activity of its urease enzyme for colonization of the gastric mucosa. The transcription, expression, and activity of H. pylori urease were previously demonstrated to be induced by nickel supplementation of growth media. Here it is demonstrated that the HP1338 protein, an ortholog of the Escherichia coli nickel regulatory protein NikR, mediates nickel-responsive induction of urease expression in H. pylori. Mutation of the HP1338 gene (nikR) of H. pylori strain 26695 resulted in significant growth inhibition of the nikR mutant in the presence of supplementation with NiCl(2) at > or =100 microM, whereas the wild-type strain tolerated more than 10-fold-higher levels of NiCl(2). Mutation of nikR did not affect urease subunit expression or urease enzyme activity in unsupplemented growth media. However, the nickel-induced increase in urease subunit expression and urease enzyme activity observed in wild-type H. pylori was absent in the H. pylori nikR mutant. A similar lack of nickel responsiveness was observed upon removal of a 19-bp palindromic sequence in the ureA promoter, as demonstrated by using a genomic ureA::lacZ reporter gene fusion. In conclusion, the H. pylori NikR protein and a 19-bp operator sequence in the ureA promoter are both essential for nickel-responsive induction of urease expression in H. pylori.
重要的人类病原体幽门螺杆菌需要其脲酶大量表达并具有活性才能在胃黏膜定植。先前已证明，在生长培养基中添加镍可诱导幽门螺杆菌脲酶的转录、表达和活性。本文证明，HP1338蛋白（大肠杆菌镍调节蛋白NikR的直系同源物）介导镍对幽门螺杆菌脲酶表达的诱导作用。幽门螺杆菌26695菌株的HP1338基因（nikR）发生突变，导致在添加≥100 microM NiCl₂的情况下，nikR突变体的生长受到显著抑制，而野生型菌株能够耐受比其高10倍以上的NiCl₂水平。在未添加镍的生长培养基中，nikR突变不影响脲酶亚基表达或脲酶活性。然而，在幽门螺杆菌nikR突变体中未观察到野生型幽门螺杆菌中镍诱导的脲酶亚基表达增加和脲酶活性增强。通过使用基因组ureA::lacZ报告基因融合体证明，去除ureA启动子中的一段19bp回文序列后也观察到类似的镍反应缺失。总之，幽门螺杆菌NikR蛋白和ureA启动子中的一段19bp操纵序列对于镍对幽门螺杆菌脲酶表达的诱导作用均至关重要。
