The Arc system is a two-component system found in some bacteria that regulates gene expression in faculatative anaerobes such as Escheria coli. Two-component system means that it has a sensor molecule and a response regulator. Arc is an abbreviation for Anoxic Redox Control system. Arc systems are instrumental in maintaining energy metabolism during transcription of bacteria. The ArcA response regulator looks at growth conditions and expresses genes to best suit the bacteria. The Arc B sensor kinase, which is a tripartite protein, is membrane bound and can autophosphorylate.
The Arc System was first reported in E. coli strains and subsequently many followed. ArcA/ArcB were first identified as playing an important role in regulation of aerobic and anaerobic pathways by Shiro Iuchi and E. C. Lin. These two scientists designed a genetic screen using the sdh-lacZ operon in a Δlac strain of E. coli. It was shown that mutations in arcA and arcB resulted in elevated levels of enzymes involved in anaerobic fermentation pathways. These two scientists are responsible for the name arc, which originally stood for aerobic respiration control.