title: Identification of a Chemoreceptor for C2 and C3 Carboxylic Acids.
abstract: Chemoreceptors are at the beginnings of chemosensory signaling cascades that mediate chemotaxis. Most bacterial chemoreceptors are functionally unannotated and are characterized by a diversity in the structure of their ligand binding domains (LBDs). The data available indicate that there are two major chemoreceptor families at the functional level, namely, those that respond to amino acids or to Krebs cycle intermediates. Since pseudomonads show chemotaxis to many different compounds and possess different types of chemoreceptors, they are model organisms to establish relationships between chemoreceptor structure and function. Here, we identify PP2861 (termed McpP) of Pseudomonas putida KT2440 as a chemoreceptor with a novel ligand profile. We show that the recombinant McpP LBD recognizes acetate, pyruvate, propionate, and l-lactate, with KD (equilibrium dissociation constant) values ranging from 34 to 107 μM. Deletion of the mcpP gene resulted in a dramatic reduction in chemotaxis toward these ligands, and complementation restored a native-like phenotype, indicating that McpP is the major chemoreceptor for these compounds. McpP has a CACHE-type LBD, and we present data indicating that CACHE-containing chemoreceptors of other species also mediate taxis to C2 and C3 carboxylic acids. In addition, the LBD of NbaY of Pseudomonas fluorescens, an McpP homologue mediating chemotaxis to 2-nitrobenzoate, bound neither nitrobenzoates nor the McpP ligands. This work provides further insight into receptor structure-function relationships and will be helpful to annotate chemoreceptors of other bacteria.
authors.affiliation: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain.
authors.forename: Vanina
authors.initials: V
authors.lastname: García
authors.affiliation: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain.
authors.forename: Jose-Antonio
authors.initials: JA
authors.lastname: Reyes-Darias
authors.affiliation: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Martín-Mora
authors.affiliation: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Morel
authors.affiliation: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Matilla
authors.affiliation: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain tino.krell@eez.csic.es.
authors.forename: Tino
authors.identifier: http://orcid.org/0000-0002-9040-3166
authors.initials: T
authors.lastname: Krell
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002264:Carboxylic Acids / Q000378:metabolism*; D002633:Chemotaxis; D017353:Gene Deletion; D005816:Genetic Complementation Test; D011551:Pseudomonas fluorescens / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D016958:Pseudomonas putida / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D002264:Carboxylic Acids