The Arc system stands for Aerobic Respiratory Control system. It is an example of a two-component system, in that it has a sensor molecule and a response regulator.

The Regulation of Various Genes

It has been determined that the Arc system regulates as many as 30 genes, with repression of the following examples: cytochrome

Cytochrome

Cytochromes are, in general, membrane-bound hemoproteins that contain heme groups and carry out electron transport.They are found either as monomeric proteins or as subunits of bigger enzymatic complexes that catalyze redox reactions....

 o oxidase, cytochrome d oxidase, and various gluconeogenic

Gluconeogenesis

Gluconeogenesis is a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates such as lactate, glycerol, and glucogenic amino acids....

 enzymes, such as for the glyoxylate cycle

Glyoxylate cycle

The glyoxylate cycle, a variation of the Tricarboxylic Acid Cycle, is an anabolic metabolic pathway occurring in plants, bacteria, protists, fungi and several microorganisms, such as E. coli and yeast. The glyoxylate cycle centers on the conversion of acetyl-CoA to succinate for the synthesis of...

, and fatty acid oxidation. It also induces the expression of Pyruvate formate lyase

Pyruvate formate lyase

Pyruvate formate lyase is an enzyme found in Escherichia coli and other organisms. It helps regulate anaerobic glucose metabolism. Using radical non-redox chemistry, it catalyzes the reversible conversion of pyruvate and coenzyme-A into formate and acetyl-CoA...

.

Mechanism of the Arc System

The Arc system uses a two component regulatory system. The sensor, ArcB, is an unusual histidine kinase

Histidine kinase

Histidine Kinases are multifunctional, typically transmembrane, proteins of the transferase class that play a role in signal transduction across the cellular membrane. The vast majority of HKs are homodimers that exhibit autokinase, phosphotransfer, and phosphatase activity. HKs can act as...

 in that it contains three signaling domains. ArcB senses the redox

Redox

Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 state of the cell, and becomes phosphorylated. The phosphate is shuttled onto various signalling domains until it winds up on ArcA, the response regulator. The phosphorylated ArcA is then able to act as either an activator

Activator

Activator may mean:* Activator , a DNA-binding protein that regulates one or more genes by increasing the rate of transcription* Activator , a type of effector that increases the rate of enzyme mediated reactions...

 or repressor

Repressor

In molecular genetics, a repressor is a DNA-binding protein that regulates the expression of one or more genes by binding to the operator and blocking the attachment of RNA polymerase to the promoter, thus preventing transcription of the genes. This blocking of expression is called...

 for various metabolic genes. So, when oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

is low, then gene products that utilize oxygen will be repressed, while genes that do not require oxygen will be upregulated.