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Aromatic Acid

The Experts below are selected from a list of 204 Experts worldwide ranked by ideXlab platform

Caroline S Harwood – 1st expert on this subject based on the ideXlab platform

  • pcak a high affinity permease for the Aromatic compounds 4 hydroxybenzoate and protocatechuate from pseudomonas putida
    Journal of Bacteriology, 1997
    Co-Authors: Nancy N Nichols, Caroline S Harwood

    Abstract:

    PcaK is a transporter and chemoreceptor protein from Pseudomonas putida that is encoded as part of the beta-ketoadipate pathway regulon for Aromatic Acid degradation. When expressed in Escherichia coli, PcaK was localized to the membrane and catalyzed the accumulation of two Aromatic substrates, 4-hydroxybenzoate and protocatechuate, against a concentration gradient. Benzoate inhibited 4-hydroxybenzoate uptake but was not a substrate for PcaK-catalyzed transport. A P. putida pcaK mutant was defective in its ability to accumulate micromolar amounts of 4-hydroxybenzoate and protocatechuate. The mutant was also impaired in growth on millimolar concentrations of these Aromatic Acids. In contrast, the pcaK mutant grew at wild-type rates on benzoate. The Vmax for uptake of 4-hydroxybenzoate was at least 25 nmol/min/mg of protein, and the Km was 6 microM. PcaK-mediated transport is energized by the proton motive force. These results show that although Aromatic Acids in the undissociated (uncharged) form can diffuse across bacterial membranes, high-specificity active transport systems probably also contribute to the ability of bacteria to grow on the micromolar concentrations of these compounds that are typically present in soil. A variety of Aromatic molecules, including naturally occurring lignin derivatives and xenobiotics, are metabolized by bacteria and may be substrates for transport proteins. The characterization of PcaK provides a foundation for understanding active transport as a critical step in the metabolism of Aromatic carbon sources.

  • identification of the pcarkf gene cluster from pseudomonas putida involvement in chemotaxis biodegradation and transport of 4 hydroxybenzoate
    Journal of Bacteriology, 1994
    Co-Authors: Caroline S Harwood, Nancy N Nichols, Jayna L Ditty, Rebecca E Parales

    Abstract:

    Pseudomonas putida PRS2000 is chemotactic to 4-hydroxybenzoate and other Aromatic Acids. This behavioral response is induced when cells are grown on 4-hydroxybenzoate or benzoate, compounds that are degraded via the beta-ketoadipate pathway. Isolation of a transposon mutant defective in 4-hydroxybenzoate chemotaxis allowed identification of a new gene cluster designated pcaRKF. DNA sequencing, mutational analysis, and complementation studies revealed that pcaR encodes a regulatory protein required for induction of at least four of the enzymes of the beta-ketoadipate pathway and that pcaF encodes beta-ketoadipyl-coenzyme A thiolase, the last enzyme in the pathway. The third gene, pcaK, encodes a transporter for 4-hydroxybenzoate, and this protein is also required for chemotaxis to Aromatic Acids. The predicted PcaK protein is 47 kDa in size, with a deduced amino Acid sequence indicative of membership in the major facilitator superfamily of transport proteins. The protein, expressed in Escherichia coli, catalyzed 4-hydroxybenzoate transport. In addition, whole cells of P. putida pcaK mutants accumulated 4-hydroxybenzoate at reduced rates compared with that in wild-type cells. The pcaK mutation did not impair growth at the expense of 4-hydroxybenzoate under most conditions; however, mutant cells grew somewhat more slowly than the wild type on 4-hydroxybenzoate at a high pH. The finding that 4-hydroxybenzoate chemotaxis can be disrupted without an accompanying effect on metabolism indicates that this chemotactic response is receptor mediated. It remains to be determined, however, whether PcaK itself is a chemoreceptor for 4-hydroxybenzoate or whether it plays an indirect role in chemotaxis. These findings indicate that Aromatic Acid detection and transport are integral features of Aromatic degradation pathways. Images

  • Regulation of the pcaIJ genes for Aromatic Acid degradation in Pseudomonas putida.
    Journal of Bacteriology, 1993
    Co-Authors: Rebecca E Parales, Caroline S Harwood

    Abstract:

    Six of the genes encoding enzymes of the beta-ketoadipate pathway for benzoate and 4-hydroxybenzoate degradation in Pseudomonas putida are organized into at least three separate transcriptional units. As an initial step to defining this pca regulon at the molecular level, lacZ fusions were made with the pcaI and pcaJ genes, which encode the two subunits of beta-ketoadipate:succinyl-coenzyme A transferase, the enzyme catalyzing the next-to-last step in the beta-ketoadipate pathway. Fusion analyses showed that pcaI and pcaJ constitute an operon which requires beta-ketoadipate or its nonmetabolizable analog, adipate, as well as the pcaR regulatory gene for induction. The pcaIJ promoter is likely to be a sigma 70-type promoter; it has a sigma 70-type consensus sequence and did not require the alternative sigma factor, RpoN, for induction. Deletion analysis of the promoter region of a pcaI-lacZ transcriptional fusion indicated that no specific DNA sequences upstream of the -35 region were required for full induction. This implies that the binding site for the activator protein, PcaR, is unusually close to the transcriptional start site of pcaIJ.

Rebecca E Parales – 2nd expert on this subject based on the ideXlab platform

  • identification of the pcarkf gene cluster from pseudomonas putida involvement in chemotaxis biodegradation and transport of 4 hydroxybenzoate
    Journal of Bacteriology, 1994
    Co-Authors: Caroline S Harwood, Nancy N Nichols, Jayna L Ditty, Rebecca E Parales

    Abstract:

    Pseudomonas putida PRS2000 is chemotactic to 4-hydroxybenzoate and other Aromatic Acids. This behavioral response is induced when cells are grown on 4-hydroxybenzoate or benzoate, compounds that are degraded via the beta-ketoadipate pathway. Isolation of a transposon mutant defective in 4-hydroxybenzoate chemotaxis allowed identification of a new gene cluster designated pcaRKF. DNA sequencing, mutational analysis, and complementation studies revealed that pcaR encodes a regulatory protein required for induction of at least four of the enzymes of the beta-ketoadipate pathway and that pcaF encodes beta-ketoadipyl-coenzyme A thiolase, the last enzyme in the pathway. The third gene, pcaK, encodes a transporter for 4-hydroxybenzoate, and this protein is also required for chemotaxis to Aromatic Acids. The predicted PcaK protein is 47 kDa in size, with a deduced amino Acid sequence indicative of membership in the major facilitator superfamily of transport proteins. The protein, expressed in Escherichia coli, catalyzed 4-hydroxybenzoate transport. In addition, whole cells of P. putida pcaK mutants accumulated 4-hydroxybenzoate at reduced rates compared with that in wild-type cells. The pcaK mutation did not impair growth at the expense of 4-hydroxybenzoate under most conditions; however, mutant cells grew somewhat more slowly than the wild type on 4-hydroxybenzoate at a high pH. The finding that 4-hydroxybenzoate chemotaxis can be disrupted without an accompanying effect on metabolism indicates that this chemotactic response is receptor mediated. It remains to be determined, however, whether PcaK itself is a chemoreceptor for 4-hydroxybenzoate or whether it plays an indirect role in chemotaxis. These findings indicate that Aromatic Acid detection and transport are integral features of Aromatic degradation pathways. Images

  • Regulation of the pcaIJ genes for Aromatic Acid degradation in Pseudomonas putida.
    Journal of Bacteriology, 1993
    Co-Authors: Rebecca E Parales, Caroline S Harwood

    Abstract:

    Six of the genes encoding enzymes of the beta-ketoadipate pathway for benzoate and 4-hydroxybenzoate degradation in Pseudomonas putida are organized into at least three separate transcriptional units. As an initial step to defining this pca regulon at the molecular level, lacZ fusions were made with the pcaI and pcaJ genes, which encode the two subunits of beta-ketoadipate:succinyl-coenzyme A transferase, the enzyme catalyzing the next-to-last step in the beta-ketoadipate pathway. Fusion analyses showed that pcaI and pcaJ constitute an operon which requires beta-ketoadipate or its nonmetabolizable analog, adipate, as well as the pcaR regulatory gene for induction. The pcaIJ promoter is likely to be a sigma 70-type promoter; it has a sigma 70-type consensus sequence and did not require the alternative sigma factor, RpoN, for induction. Deletion analysis of the promoter region of a pcaI-lacZ transcriptional fusion indicated that no specific DNA sequences upstream of the -35 region were required for full induction. This implies that the binding site for the activator protein, PcaR, is unusually close to the transcriptional start site of pcaIJ.

Nancy N Nichols – 3rd expert on this subject based on the ideXlab platform

  • pcak a high affinity permease for the Aromatic compounds 4 hydroxybenzoate and protocatechuate from pseudomonas putida
    Journal of Bacteriology, 1997
    Co-Authors: Nancy N Nichols, Caroline S Harwood

    Abstract:

    PcaK is a transporter and chemoreceptor protein from Pseudomonas putida that is encoded as part of the beta-ketoadipate pathway regulon for Aromatic Acid degradation. When expressed in Escherichia coli, PcaK was localized to the membrane and catalyzed the accumulation of two Aromatic substrates, 4-hydroxybenzoate and protocatechuate, against a concentration gradient. Benzoate inhibited 4-hydroxybenzoate uptake but was not a substrate for PcaK-catalyzed transport. A P. putida pcaK mutant was defective in its ability to accumulate micromolar amounts of 4-hydroxybenzoate and protocatechuate. The mutant was also impaired in growth on millimolar concentrations of these Aromatic Acids. In contrast, the pcaK mutant grew at wild-type rates on benzoate. The Vmax for uptake of 4-hydroxybenzoate was at least 25 nmol/min/mg of protein, and the Km was 6 microM. PcaK-mediated transport is energized by the proton motive force. These results show that although Aromatic Acids in the undissociated (uncharged) form can diffuse across bacterial membranes, high-specificity active transport systems probably also contribute to the ability of bacteria to grow on the micromolar concentrations of these compounds that are typically present in soil. A variety of Aromatic molecules, including naturally occurring lignin derivatives and xenobiotics, are metabolized by bacteria and may be substrates for transport proteins. The characterization of PcaK provides a foundation for understanding active transport as a critical step in the metabolism of Aromatic carbon sources.

  • identification of the pcarkf gene cluster from pseudomonas putida involvement in chemotaxis biodegradation and transport of 4 hydroxybenzoate
    Journal of Bacteriology, 1994
    Co-Authors: Caroline S Harwood, Nancy N Nichols, Jayna L Ditty, Rebecca E Parales

    Abstract:

    Pseudomonas putida PRS2000 is chemotactic to 4-hydroxybenzoate and other Aromatic Acids. This behavioral response is induced when cells are grown on 4-hydroxybenzoate or benzoate, compounds that are degraded via the beta-ketoadipate pathway. Isolation of a transposon mutant defective in 4-hydroxybenzoate chemotaxis allowed identification of a new gene cluster designated pcaRKF. DNA sequencing, mutational analysis, and complementation studies revealed that pcaR encodes a regulatory protein required for induction of at least four of the enzymes of the beta-ketoadipate pathway and that pcaF encodes beta-ketoadipyl-coenzyme A thiolase, the last enzyme in the pathway. The third gene, pcaK, encodes a transporter for 4-hydroxybenzoate, and this protein is also required for chemotaxis to Aromatic Acids. The predicted PcaK protein is 47 kDa in size, with a deduced amino Acid sequence indicative of membership in the major facilitator superfamily of transport proteins. The protein, expressed in Escherichia coli, catalyzed 4-hydroxybenzoate transport. In addition, whole cells of P. putida pcaK mutants accumulated 4-hydroxybenzoate at reduced rates compared with that in wild-type cells. The pcaK mutation did not impair growth at the expense of 4-hydroxybenzoate under most conditions; however, mutant cells grew somewhat more slowly than the wild type on 4-hydroxybenzoate at a high pH. The finding that 4-hydroxybenzoate chemotaxis can be disrupted without an accompanying effect on metabolism indicates that this chemotactic response is receptor mediated. It remains to be determined, however, whether PcaK itself is a chemoreceptor for 4-hydroxybenzoate or whether it plays an indirect role in chemotaxis. These findings indicate that Aromatic Acid detection and transport are integral features of Aromatic degradation pathways. Images