title: Characterization of Bradyrhizobium japonicum pcaBDC genes involved in 4-hydroxybenzoate degradation.
abstract: The pca structural genes encode enzymes that participate in the conversion of protocatechuate to succinate and acetylcoenzyme A. A 3. 05-kb region of the Bradyrhizobium japonicum strain USDA110 genome has been characterized, which contains the pcaB, pcaD and pcaC genes. The predicted protein sequences of the three genes have extensive homologies with beta-carboxy-cis,cis-muconate cycloisomerase (PcaB), beta-ketodiapate enol-lactone hydrolase (PcaD), and gamma-carboxymuconolactone decarboxylase (PcaC), respectively, from Acinetobacter calcoaceticus and Pseudomonas putida. The DNA sequence revealed that the pca genes are probably arranged in a single transcriptional unit, pcaBDC, similar to that described in P. putida. A pcaB deletion mutant constructed by marker exchange mutagenesis lost the ability to use 4-hydroxybenzoate or protocatechuate as the only carbon source, demonstrating functionality of the characterized genes in catabolism of hydroxyaromatics by B. japonicum. Furthermore, 4-hydroxybenzoate and protocatechuate became toxic for the pcaB mutant, indicating that hydroxyaromatics catabolism serves both nutritional and detoxifying purposes.
authors.affiliation: Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, P.O. Box 419, 18080-Granada, Spain.
authors.forename: M J
authors.initials: MJ
authors.lastname: Lorite
authors.forename: J
authors.initials: J
authors.lastname: Sanjuan
authors.forename: L
authors.initials: L
authors.lastname: Velasco
authors.forename: J
authors.initials: J
authors.lastname: Olivares
authors.forename: E J
authors.initials: EJ
authors.lastname: Bedmar
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001565:Benzoates / Q000378:metabolism; D019817:Benzoic Acid; D001673:Biodegradation, Environmental; D002262:Carboxy-Lyases / Q000235:genetics / Q000378:metabolism; D002265:Carboxylic Ester Hydrolases / Q000235:genetics / Q000378:metabolism; D002874:Chromosome Mapping; D004269:DNA, Bacterial / Q000235:genetics; D017353:Gene Deletion; D005798:Genes, Bacterial; D019753:Intramolecular Lyases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010226:Parabens / Q000378:metabolism*; D012230:Rhizobiaceae / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001565:Benzoates; D004269:DNA, Bacterial; D010226:Parabens; D019817:Benzoic Acid; D002265:Carboxylic Ester Hydrolases; C021927:3-oxoadipate enol-lactonase; D002262:Carboxy-Lyases; C019832:4-carboxymuconolactone decarboxylase; D019753:Intramolecular Lyases; C019830:3-carboxy-cis-cis-muconate cycloisomerase; C038193:4-hydroxybenzoic acid