Effect of d -Lactate on the Physiological Activity of the ArcB Sensor Kinase in Escherichia coli

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 the respiratory growth conditions. Under anoxic growth conditions ArcB autophosphorylates and transphosphorylates ArcA, which in turn represses or activates its target operons. The anaerobic metabolite D-lactate has been shown to stimulate the in vitro autophosphorylating activity of ArcB. In this study, the in vivo effect of D-lactate on the kinase activity of ArcB was assessed. The results demonstrate that D-lactate does not act as a direct signal for activation of ArcB, as previously proposed, but acts as a physiologically significant effector that amplifies ArcB kinase activity.The Arc (anoxic redox control) two-component system is an important element in the complex transcriptional regulatory network that allows facultative anaerobic bacteria, such as Escherichia coli, to sense various respiratory growth conditions and adapt their gene expression accordingly (13,15,22). This system consists of the transmembrane sensor kinase ArcB and the cognate response regulator ArcA. The ArcB protein belongs to a subfamily of tripartite hybrid kinases, because it contains three catalytic domains: an N-terminal transmitter domain (H1) with a conserved His292 residue, a central receiver domain (D1) with a conserved Asp576 residue, and a C-terminal phosphotransfer domain (H2) with a conserved His717 residue (10, 15). Under reducing conditions, ArcB autophosphorylates at the expense of ATP and transphosphorylates ArcA via a His2923Asp5763His7173Asp54 phosphorelay (8,19). Phosphorylated ArcA (ArcA-P), in turn, represses the expression of many operons involved in respiratory metabolism and activates a few operons encoding proteins involved in fermentative metabolism (22,23). Under oxidizing conditions ArcB autophosphorylation is inhibited by the quinone electron carriers (7), and ArcA-P dephosphorylates via a reverse Asp543His7173Asp576 phosphorelay (8). Signal transduction by phosphorelay has also been reported for the Kin/Spo system of Bacillus subtilis (4), the BvgS/BvgA system of Bordetella pertussis (29), the TorS/TorR system of E. coli (16), and the Sln1p/Ypd1p/Ssk1p system of Saccharomyces cerevisiae (28). This complex phosphotransfer mechanism is believed to allow multiple levels of control for fine-tuning.It has been reported previously that the presence of certain fermentation intermediates, such as D-lactate, acetate, and pyruvate, accelerates the autophosphorylation activity of ArcB and enhances the subsequent transphosphorylation of ArcA (6, 11). However, no in vivo evidence has been obtained to support the physiological significance of such an effect. Furthermore, because the cellular metabolites mentioned above accumulate during anaerobiosis, it has been proposed that these compounds might act as the actual signals through which ArcB senses anaerobic environments in vivo (2, 11).Here we present the results of experiments designed to probe the in vivo effect of...

Identification of a quinone-sensitive redox switch in the ArcB sensor kinase

“…Under reducing conditions, ArcB undergoes ATP-dependent autophosphorylation, a process shown to be enhanced by certain anaerobic metabolites such as D-lactate, acetate, and pyruvate (10,11), and transphosphorylates ArcA via a His-292 3 Asp-576 3 His-717 3 Asp-54 phosphorelay (12,13). Phosphorylated ArcA (ArcA-P), in turn, represses the expression of many operons involved in respiratory metabolism and activates a few operons encoding proteins involved in fermentative metabolism (4,14,15).…”

Requirement of the Receiver and Phosphotransfer Domains of ArcB for Efficient Dephosphorylation of Phosphorylated ArcA In Vivo

“…Under reducing conditions, ArcB undergoes ATP-dependent autophosphorylation (10,16), a process that is enhanced by certain anaerobic metabolites such as D-lactate, acetate, and pyruvate (7,30), and transphosphorylates ArcA via a His292 3 Asp576 3 His717 3 Asp54 phosphorelay (10,18). Phosphorylated ArcA (ArcA-P), in turn, represses the expression of many operons involved in respiratory metabolism and activates a few operons encoding proteins involved in fermentative metabolism (23).…”

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).…”