PMID:9603882
| Citation |
Díaz, E, Ferrández, A and García, JL (1998) Characterization of the hca cluster encoding the dioxygenolytic pathway for initial catabolism of 3-phenylpropionic acid in Escherichia coli K-12. J. Bacteriol. 180:2915-23 |
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| Abstract |
We have identified, cloned, and sequenced the hca cluster encoding the dioxygenolytic pathway for initial catabolism of 3-phenylpropionic acid (PP) in Escherichia coli K-12. This cluster maps at min 57.5 of the chromosome and is composed of five catabolic genes arranged as a putative operon (hcaA1A2CBD) and two additional genes transcribed in the opposite direction that encode a potential permease (hcaT) and a regulator (hcaR). Sequence comparisons revealed that while hcaA1A2CD genes encode the four subunits of the 3-phenylpropionate dioxygenase, the hcaB gene codes for the corresponding cis-dihydrodiol dehydrogenase. This type of catabolic module is homologous to those encoding class IIB dioxygenases and becomes the first example of such a catabolic cluster in E. coli. The inducible expression of the hca genes requires the presence of the hcaR gene product, which acts as a transcriptional activator and shows significant sequence similarity to members of the LysR family of regulators. Interestingly, the HcaA1A2CD and HcaB enzymes are able to oxidize not only PP to 3-(2,3-dihydroxyphenyl)propionate (DHPP) but also cinnamic acid (CI) to its corresponding 2, 3-dihydroxy derivative. Further catabolism of DHPP requires the mhp-encoded meta fission pathway for the mineralization of 3-hydroxyphenylpropionate (3HPP) (A. Ferrández, J. L. García, and E. Díaz, J. Bacteriol. 179:2573-2581, 1997). Expression in Salmonella typhimurium of the mhp genes alone or in combination with the hca cluster allowed the growth of the recombinant bacteria in 3-hydroxycinnamic acid (3HCI) and CI, respectively. Thus, the convergent mhp- and hca-encoded pathways are also functional in S. typhimurium, and they are responsible for the catabolism of different phenylpropanoid compounds (3HPP, 3HCI, PP, and CI) widely available in nature. |
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| Keywords |
Amino Acid Sequence; Base Sequence; Cloning, Molecular; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli Proteins; Genes, Bacterial/genetics; Membrane Transport Proteins/genetics; Models, Chemical; Molecular Sequence Data; Multigene Family/genetics; Organic Anion Transporters; Oxidoreductases/genetics; Oxidoreductases/metabolism; Oxygenases/genetics; Oxygenases/metabolism; Phenylpropionates/metabolism; Receptors, Cytoplasmic and Nuclear/genetics; Restriction Mapping; Sequence Analysis, DNA; Trans-Activators/genetics; Transcription Factors |
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