Member of the two-component regulatory system AtoS/AtoC. In the presence of acetoacetate, AtoS/AtoC stimulates the expression of the atoDAEB operon, leading to short chain fatty acid catabolism and activation of the poly-(R)-3-hydroxybutyrate (cPHB) biosynthetic pathway. Also induces the operon in response to spermidine (PubMed:2883171, PubMed:16153782, PubMed:16564134, PubMed:17475408). Involved in the regulation of motility and chemotaxis, via transcriptional induction of the flagellar regulon (PubMed:22083893). AtoC acts by binding directly to the promoter region of the target genes (PubMed:17616594). In addition to its role as a transcriptional regulator, functions as a post-translational regulator that inhibits polyamine biosynthesis via regulation of ornithine decarboxylase (ODC) (PubMed:8346225). Membrane-associated in the presence of AtoS. Phosphorylated by AtoS (PubMed:16153782). Contains two phosphorylation sites, which are both involved in the transduction of the acetoacetate signal (PubMed:16153782). Asp-55 is probably the primary phosphorylation site, but either both residues can be phosphorylated independently by AtoS or the phosphate group can be transferred between them (PubMed:16153782). The N-terminus is blocked. Deletion of the atoSC locus renders cells not motile or responsive against any chemoattractant or repellent independently of the atoSC inducer's presence.