Member of the two-component regulatory system ArcB/ArcA. Represses a wide variety of aerobic enzymes under anaerobic conditions. It also may be involved in the osmoregulation of envelope proteins. When activated by ArcB, it negatively regulates the expression of genes of aerobic function. Activates the transcription of the plfB operon by binding to its promoter (By similarity). Phosphorylated by ArcB.