title: The ArcBA two-component system of Escherichia coli is regulated by the redox state of both the ubiquinone and the menaquinone pool.
abstract: ArcBA is a two-component regulatory system of Escherichia coli involved in sensing oxygen availability and the concomitant transcriptional regulation of oxidative and fermentative catabolism. Based on in vitro data, it has been postulated that the redox state of the ubiquinone pool is the determinant for ArcB kinase activity. Here we report on the in vivo regulation of ArcB activation, as determined using a lacZ reporter specifically responsive to phosphorylated ArcA. Our results indicate that upon deletion of a ubiquinone biosynthetic enzyme, regulation of ArcB in the anaerobic-aerobic transition is not affected. In contrast, interference with menaquinone biosynthesis leads to inactivation of ArcB during anaerobic growth; this phenotype is fully rescued by addition of a menaquinone precursor. This clearly demonstrates that the menaquinones play a major role in ArcB activation. ArcB shows a complex pattern of regulation when E. coli is titrated through the entire aerobiosis range; ArcB is activated under anaerobic and subaerobic conditions and is much less active under fully aerobic and microaerobic conditions. Furthermore, there is no correlation between ArcB activation and the redox state of the ubiquinone pool, but there is a restricted correlation between the total cellular ubiquinone content and ArcB activity due to the considerable increase in the size of the ubiquinone pool with increasing degrees of aerobiosis. These results lead to the working hypothesis that the in vivo activity of ArcB in E. coli is modulated by the redox state of the menaquinone pool and that the ubiquinone/ubiquinol ratio in vivo surely is not the only determinant of ArcB activity.
authors.affiliation: Swammerdam Institute for Life Sciences-Molecular Microbial Physiology, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands.
authors.forename: Martijn
authors.initials: M
authors.lastname: Bekker
authors.forename: Svetlana
authors.initials: S
authors.lastname: Alexeeva
authors.forename: Wouter
authors.initials: W
authors.lastname: Laan
authors.forename: Gary
authors.initials: G
authors.lastname: Sawers
authors.forename: Joost
authors.initials: J
authors.lastname: Teixeira de Mattos
authors.forename: Klaas
authors.initials: K
authors.lastname: Hellingwerf
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D024202:Electrophoretic Mobility Shift Assay; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008957:Models, Genetic; D009876:Operon / Q000235:genetics; D010084:Oxidation-Reduction; D010766:Phosphorylation; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014451:Ubiquinone / Q000378:metabolism*; D024482:Vitamin K 2 / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D012097:Repressor Proteins; C041610:arcA protein, E coli; D024482:Vitamin K 2; D014451:Ubiquinone; D011494:Protein Kinases; C065271:arcB protein, E coli