Ubiquinone and Menaquinone Electron Carriers Represent the Yin and Yang in the Redox Regulation of the ArcB Sensor Kinase

Abstract

The Arc two-component system, comprising the ArcB sensor kinase and the ArcA response regulator, modulates the expression of numerous genes in response to respiratory growth conditions. Under aerobic growth conditions, the ubiquinone electron carriers were proposed to silence the kinase activity of ArcB by oxidizing two cytosol-located redox-active cysteine residues that participate in intermolecular disulfide bond formation. Here, we confirm the role of the ubiquinone electron carriers as the silencing signal of ArcB in vivo, we show that the redox potential of ArcB is about ؊41 mV, and we demonstrate that the menaquinols are required for proper ArcB activation upon a shift from aerobic to anaerobic growth conditions. Thus, an essential link in the Arc signal transduction pathway connecting the redox state of the quinone pool to the transcriptional apparatus is elucidated. The Arc (anoxic redox control) two-component system (TCS) is a key element in the transcriptional regulatory network that allows facultative anaerobic bacteria to sense various respiratory growth conditions and adapt their gene expression accordingly (1-4). This system comprises the cytoplasmic response regulator ArcA and the membrane-anchored sensor kinase ArcB (5, 6). ArcA is a typical response regulator possessing an N-terminal receiver domain with a conserved Asp residue at position 54 and a C-terminal helix-turn-helix DNA binding domain. In contrast, ArcB is an unorthodox sensor kinase, having a very short periplasmic sequence of only 16 amino acid residues delimited by two canonical transmembrane segments. Interestingly, these segments of ArcB do not directly participate in signal sensing but, rather, serve as an anchor that keeps the protein close to the source of the signal (7). Moreover, ArcB contains three catalytic domains: an N-terminal transmitter domain with a conserved His292 residue, a central receiver domain with a conserved Asp576 residue, and a C-terminal phosphotransfer domain with a conserved His717 residue (6,8). Finally, in the linker, that is, the region connecting the catalytic domains with the transmembrane domain, there are a functional leucine zipper (9) and a PAS domain (10).Under reducing conditions, ArcB autophosphorylates through an intramolecular reaction (11), a process shown to be enhanced by certain anaerobic metabolites, such as D-lactate, acetate, and pyruvate (12, 13), and transphosphorylates ArcA via a His292 ¡ Asp576 ¡ His717 ¡ Asp54 phosphorelay (14, 15). Phosphorylated ArcA (ArcA-P), in turn, represses the expression of many operons involved in respiratory metabolism and activates others encoding proteins involved in fermentative metabolism (16)(17)(18)(19). Under nonstimulating conditions, ArcB acts as a specific ArcA-P phosphatase that catalyzes the dephosphorylation of ArcA-P by a reverse Asp54 ¡ His717 ¡ Asp576 ¡ Pi phosphorelay (20, 21). Previously, it was reported that regulation of the catalytic activity of ArcB is set by rotational movements that alter the orientation of the cytosolic portion...

Systematic Analysis of Two-Component Systems in Citrobacter rodentium Reveals Positive and Negative Roles in Virulence

“…4). The ArcAB TCS is known to control the transition from aerobic growth to microaerobic or anaerobic growth in response to the redox status of the ubiquinone electron carriers (46). Therefore, a functional ArcAB TCS appears to be required for bacterial adaptation to the anaerobic environment of the mouse large intestine.…”

Alkali Metals in Addition to Acidic pH Activate the EvgS Histidine Kinase Sensor in Escherichia coli

“…Under aerobic growth conditions, the ubiquinone electron carriers are proposed to silence the kinase activity of ArcB by oxidizing two PAS-located redox-active cysteine residues (C 180 and C 241 ) that participate in intermolecular disulfide bond formation (39,40). On the other hand, the menaquinone electron carriers are required for activation of ArcB upon a shift from aerobic to anaerobic growth conditions (41). The in vitro autophosphorylation activity of the cytoplasmic BvgS and EvgS (without the periplasmic and transmembrane region) kinase was also inhibited by oxidized ubiquinone and not by other electron carriers such as menaquinone, NAD, and flavin adenine dinucleotide (FAD) (38).…”

Adaptation of anaerobic cultures of Escherichia coli K‐12 in response to environmental trimethylamine‐N‐oxide

“…The transient decrease in ArcA activity emphasizes the complexity of the ArcBA response. At least three signals have been proposed as modulators of ArcB activity: oxidized ubiquinone acts negatively; reduced menaquinone acts positively; and fermentation products, such as acetate, promote ArcB kinase activity and ArcA phosphorylation (Georgellis et al ., 1999; 2001; Rodriguez et al ., 2004; Bekker et al ., 2010; Rolfe et al ., 2011; 2012; Alvarez et al ., 2013). The dynamics of ArcA activity reported here suggests that introduction of TMAO to the fermenting culture causes net oxidation of the menaquinone pool, resulting in the initial dephosphorylation of ArcA followed by restoration of ArcA activity, in the final TMAO‐respiratory/fermentative steady state, perhaps mediated by enhanced production of acetate (Table 2).…”