Analysis of catRABC operon for catechol degradation from phenol-degrading Rhodococcus erythropolis

Area of Science:

• Microbial biochemistry and genetics
• Bacterial catabolism and gene regulation

Background:

• The catRABC gene cluster in Rhodococcus erythropolis CCM2595 is crucial for catechol degradation.
• This cluster encodes key enzymes: catechol 1,2-dioxygenase (CatA), cis,cis-muconate cycloisomerase (CatB), and muconolactone isomerase (CatC).
• It also includes catR, coding for an IclR-type transcriptional regulator.

Purpose of the Study:

• To elucidate the transcriptional regulation of the catRABC gene cluster in Rhodococcus erythropolis.
• To identify the specific inducers and repressors of catechol 1,2-dioxygenase gene (catA) expression.
• To characterize the role of the CatR regulator in controlling the operon.

Main Methods:

• Isolation and characterization of the catRABC gene cluster.
• Enzyme activity assays to measure catechol 1,2-dioxygenase.
• Primer extension analysis to determine transcription start points and promoter localization.
• Transcriptional fusion with the gfpuv reporter gene to measure promoter activity.
• Gene deletion studies (Rhodococcus erythropolis DeltacatR).

Main Results:

• Phenol induces catA expression, while catechol and cis,cis-muconate do not.
• Succinate represses catechol 1,2-dioxygenase activity; glucose has no effect.
• The CatR repressor binds to both P-catR and P-catA promoters.
• Phenol induction of P-catA occurs even without CatR.
• Potential binding sites for CatR and CRP were identified in the intergenic region.

Conclusions:

• The catR-catABC operon expression is primarily regulated at the transcriptional level by CatR.
• CatR acts as a repressor for both catR and catA promoters.
• Phenol is a specific inducer of catA, and its induction mechanism involves overcoming CatR-mediated repression.