title: Paralogous chemoreceptors mediate chemotaxis towards protein amino acids and the non-protein amino acid gamma-aminobutyrate (GABA).
abstract: The paralogous receptors PctA, PctB and PctC of Pseudomonas aeruginosa were reported to mediate chemotaxis to amino acids, intermediates of amino acid metabolism and chlorinated hydrocarbons. We show that the recombinant ligand binding regions (LBRs) of PctA, PctB and PctC bind 17, 5 and 2 l-amino acids respectively. In addition, PctC-LBR recognized GABA but not any other structurally related compound. l-Gln, one of the three amino acids that is not recognized by PctA-LBR, was the most tightly binding ligand to PctB suggesting that PctB has evolved to mediate chemotaxis primarily towards l-Gln. Bacteria were efficiently attracted to l-Gln and GABA, but mutation of pctB and pctC, respectively, abolished chemoattraction. The physiological relevance of taxis towards GABA is proposed to reside in an interaction with plants. LBRs were predicted to adopt double PDC (PhoQ/DcuS/CitA) like structures and site-directed mutagenesis studies showed that ligands bind to the membrane-distal module. Analytical ultracentrifugation studies have shown that PctA-LBR and PctB-LBR are monomeric in the absence and presence of ligands, which is in contrast to the enterobacterial receptors that require sensor domain dimers for ligand recognition.
authors: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, C/ Prof. Albareda, 1, 18008, Granada, Spain.
authors: Miriam
authors: M
authors: Rico-Jiménez
authors: Francisco
authors: F
authors: Muñoz-Martínez
authors: Cristina
authors: C
authors: García-Fontana
authors: Matilde
authors: M
authors: Fernandez
authors: Bertrand
authors: B
authors: Morel
authors: Alvaro
authors: A
authors: Ortega
authors: Juan Luis
authors: JL
authors: Ramos
authors: Tino
authors: T
authors: Krell
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002633:Chemotaxis; D055786:Gene Knockout Techniques; D016297:Mutagenesis, Site-Directed; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; C110124:PctA protein, Pseudomonas aeruginosa; C110122:PctB protein, Pseudomonas aeruginosa; C110123:PctC protein, Pseudomonas aeruginosa