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

Abstract

Escherichia coli senses and signals anoxic or low redox conditions in its growth environment by the Arc two-component system. Under anaerobic conditions, the ArcB sensor kinase autophosphorylates and transphosphorylates ArcA, a global transcriptional regulator that controls the expression of numerous operons involved in respiratory or fermentative metabolism. Under aerobic conditions, the kinase activity of ArcB is inhibited by the quinone electron carriers that act as direct negative signals. Here, we show that the molecular mechanism of kinase silencing involves the oxidation of two cytosol-located redox-active cysteine residues that participate in intermolecular disulfide bond formation, a reaction in which the quinones provide the source of oxidative power. Thus, a pivotal link in the Arc signal transduction pathway connecting the redox state of the quinone pool to the transcriptional apparatus is elucidated.T wo-component signal transduction systems are widespread in prokaryotes and play extensive roles in adaptation to environmental changes (1, 2). 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 (3). This system comprises the cytoplasmic response regulator ArcA and the transmembrane sensor kinase ArcB (4, 5). 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 as manifested by its unusually elaborate architecture. As a sensor, ArcB is deviant because in contrast to typical sensor kinases that have a substantial periplasmic domain for environmental sensing, ArcB has a very short periplasmic sequence of only 16 amino acid residues delimited by two canonical transmembrane segments. Interestingly, the ArcB transmembrane domain (amino acids 22-77) does not directly participate in signal sensing but rather serves as an anchor that keeps the protein close to the source of the signal (6). As a kinase, ArcB is atypical because it contains three catalytic domains: an N-terminal transmitter domain with a conserved His-292 residue, a central receiver domain with a conserved Asp-576 residue, and a C-terminal phosphotransfer domain with a conserved His-717 residue (5, 7). Moreover, in the linker that is the region connecting the catalytic domains with the transmembrane domain, there are a putative leucine zipper (8) and a Per-Arnt-Sim (PAS) domain (9).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 invo...

Structural Analysis and Solution Studies of the Activated Regulatory Domain of the Response Regulator ArcA: A Symmetric Dimer Mediated by the α4-β5-α5 Face

“…ArcA N was spun at 27 and 33 K rpm resulting in a total of six data sets that were simultaneously fit to a single species model using the program NONLIN. 53 The quality of the fit was good with an rmsd value of 5.9577E-3 and a converged molecular weight value of 13,541 [12,996,14,072] which agrees well with the theoretical value of 13,989 g/mol (bracketed values represent 95% confidence intervals).…”

“…These catalytic domains are connected to the N-terminal transmembrane region by a putative leucine zipper and a sensing PAS (Per-Arnt-Sim) domain. 12 Quinones have been identified as the redox signal sensed by this TCS 13 and more recently a model for a quinone-sensitive redox switch in the HK ArcB has been proposed. 12 The RR of this TCS is ArcA 14 , a global regulator known to control more than 30 operons involved in redox regulation (the Arc modulon).…”

“…12 Quinones have been identified as the redox signal sensed by this TCS 13 and more recently a model for a quinone-sensitive redox switch in the HK ArcB has been proposed. 12 The RR of this TCS is ArcA 14 , a global regulator known to control more than 30 operons involved in redox regulation (the Arc modulon). 15 More recently its been reported that ArcA is involved in the direct regulation of at least 55 other operons implicated in numerous cell functions and that 9% of all open reading frames in E. coli are affected directly or indirectly by phosphorylated ArcA.…”

Molecular mechanism of quinone signaling mediated through S-quinonization of a YodB family repressor QsrR

“…In Escherichia coli, the anoxic redox control ArcAB is considered a quinone-sensing two-component system (17,18). In Bacillus subtilis, the thiol-stress sensing regulator YodB is a prototypical transcriptional regulator responsible for quinone sensing and detoxification (19)(20)(21).…”

A two-component phosphotransfer network involving ArcB, ArcA, and RssB coordinates synthesis and proteolysis of σS (RpoS) in E. coli

“…Mika and R. Hengge, in prep.). (B) Upon energy starvation and/or high oxygen tension, oxidized quinones interfere with ArcB autophosphorylation (Malpica et al 2004) and RssB and ArcA get less phosphorylated. S levels increase as rpoS transcriptional repression by ArcA is relieved and S proteolysis is slowed down (since the cellular level of phosphorylated RssB is limiting for the overall rate of S degradation) (Pruteanu and Hengge-Aronis 2002).…”