Hybrid sensor kinase that regulates diverse biological functions through two distinct molecular mechanisms (PubMed:16940295). At low cell density, the extracellular concentration of the diffusible signaling factor (DSF) is below a threshold, and unphosphorylated RpfC is involved in the negative regulation of DSF synthesis, via direct interaction with the DSF synthase RpfF. Interaction prevents synthesis of DSF, which remains at a basal level. This activity does not involve the phosphorelay mechanism and is not dependent on RpfG (PubMed:11123673, PubMed:16940295). Is also member of the two-component regulatory system RpfG/RpfC, which is involved in the perception and response to DSF, which is essential for cell-cell signaling (PubMed:11123673, PubMed:12960398). At high cell density, the level of extracellular DSF increases and binding of DSF to the sensor region of RpfC causes autophosphorylation of RpfC, which results in the release of RpfF and the activation of RpfG via a four-step phosphorelay (PubMed:16940295, PubMed:28369120). Activation of RpfG leads to the positive regulation of biofilm dispersal and the production of virulence factors (PubMed:12960398). ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Binding of DSF to the sensor region causes allosteric change, which facilitates RpfC autophosphorylation. At low DSF concentrations, interacts with RpfF. Localizes at the cell poles. The N-terminal input region plays an essential role in DSF perception. DSF binds with high affinity to a 22-amino acid sensor region at the N-terminus (PubMed:28369120). The response regulatory domain, but not the HPt domain, is required for repression of DSF biosynthesis (PubMed:16940295). Autophosphorylated (PubMed:28369120). Activation may require a sequential transfer of a phosphate group from a His in the primary transmitter domain, to an Asp in the receiver domain and to a His in the secondary transmitter domain (Probable). The article describing the function has been retracted due to duplications and irregularities in some figures, but repeated experiments using the original strains support the findings.