Chemotactic-signal transducers respond to changes in the concentration of attractants and repellents in the environment, transduce a signal from the outside to the inside of the cell, and facilitate sensory adaptation through the variation of the level of methylation. Responds to L-Arg, L-Gln, L-Ala, L-Glu, L-Lys, L-Met and L-Tyr. Also involved in repellent responses to trichloroethylene (TCE), chloroform and methylthiocyanate. Monomer in the absence and presence of ligands. The ligand binding region binds directly to 5 L-amino acids. Mutant is defective in taxis toward L-Gln. Mutant shows also decreased chemotactic responses to TCE, chloroform and methylthiocyanate (PubMed:16233808, PubMed:9353923). The deletion mutant does not show significant reduction in swarming or immobilization near epithelial wounds, but the pctABC triple deletion mutant shows a significant reduction in chemotaxis and immobilization along wounds of human cystic fibrosis airway epithelial cells (PubMed:27031335). PctA has a broad ligand range and responds to most of the proteinogenic amino acids, whereas PctB and PctC have a much narrower range and show strong ligand preference for L-glutamine and gamma-aminobutyrate, respectively. These receptors are paralogs: pctA gene duplication in the common ancestor of the genus Pseudomonas led to pctC, whereas pctB originated through another, independent pctA duplication. Belongs to the methyl-accepting chemotaxis (MCP) protein family.