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 (Probable). Directly recognizes five C4-dicarboxylic acids: L-malic, citramalic, citraconic, bromosuccinic and methylsuccinic acids (PubMed:17933940, PubMed:29391435). Three of the identified ligands act as chemoattractants (L-malic, D,L-bromosuccinic and L-citramalic acids) whereas two of them (L-methylsuccinic and citraconic acids) behave as antagonists by inhibiting the downstream chemotaxis signaling cascade (PubMed:29391435). Antagonists compete with chemoattractants, thereby decreasing the affinity for chemoattractants and the subsequent chemotactic response (PubMed:29391435). Acts through the che chemosensory pathway (PubMed:29391435). Homodimer. The ligand-binding domain (LBD) is dimeric in the presence and the absence of ligands. Mutant shows a dramatic reduction in chemotaxis for all ligands, but it does not affect response to casamino acids (PubMed:29391435). Mutant showed no attraction to malate at any of the concentrations tested (PubMed:17933940). Mutation does not affect plant root colonization (PubMed:29391435). Belongs to the methyl-accepting chemotaxis (MCP) protein family.