Arc system

The Arc system stands for Anoxic 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 o oxidase, cytochrome d oxidase, and various gluconeogenic enzymes, such as for the glyoxylate cycle, and fatty acid oxidation. It also induces the expression of Pyruvate formate lyase.
Mechanism of the Arc System.
The Arc system uses a two component regulatory system. The sensor, ArcB, is an unusual histidine kinase in that it contains three signaling domains. ArcB senses the redox 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 or repressor for various metabolic genes. So, when oxygen is low, then gene products that utilize oxygen will be repressed, while genes that do not require oxygen will be upregulated.