Member of the two-component regulatory system ArsS/ArsR that regulates genes involved in biofilm formation and acid adaptation by acting on major ammonia-producing pathways (PubMed:22865848, PubMed:25997502, PubMed:27432830). Upon phosphorylation by ArsS, functions as a transcription regulator by direct binding to promoter regions of target genes including ureA, amiE and amiF to positively regulate their expression in response to acidic pH (PubMed:11751811, PubMed:16672598). Negatively autoregulates its expression (PubMed:11751811). Phosphorylated on Asp-52 by ArsS.