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Chemoreceptor (also called methyl-accepting chemotaxis protein, MCP) is the leading signal protein in the chemotaxis signaling pathway. MCP senses and binds chemoeffectors, specifically, and transmits the sensed signal to downstream proteins of the chemotaxis signaling system. The genome of <i>Agrobacterium fabrum</i> (previously, <i>tumefaciens</i>) C58 predicts that a total of 20 genes can encode MCP, but only the MCP-encoding gene <i>atu0514</i> is located inside the <i>che</i> operon. Hence, the identification of the exact function of <i>atu0514</i>-encoding chemoreceptor (here, named as MCP₅₁₄) will be very important for us to understand more deeply the chemotaxis signal transduction mechanism of <i>A. fabrum</i>. The deletion of <i>atu0514</i> significantly decreased the chemotactic migration of <i>A. fabrum</i> in a swim plate. The test of <i>atu0514</i>-deletion mutant (Δ514) chemotaxis toward single chemicals showed that the deficiency of MCP₅₁₄ significantly weakened the chemotactic response of <i>A. fabrum</i> to four various chemicals, sucrose, valine, citric acid and acetosyringone (AS), but did not completely abolish the chemotactic response. MCP₅₁₄ was localized at cell poles although it lacks a transmembrane (TM) region and is predicted to be a cytoplasmic chemoreceptor. The replacement of residue Phe328 showed that the helical structure in the hairpin subdomain of MCP₅₁₄ is a direct determinant for the cellular localization of MCP₅₁₄. Single respective replacements of key residues indicated that residues Asn336 and Val353 play a key role in maintaining the chemotactic function of MCP₅₁₄.