The Pseudomonas putida Crc Global Regulator Controls the Expression of Genes from Several Chromosomal Catabolic Pathways for Aromatic Compounds

Abstract

The Crc protein is involved in the repression of several catabolic pathways for the assimilation of some sugars, nitrogenated compounds, and hydrocarbons in Pseudomonas putida and Pseudomonas aeruginosa when other preferred carbon sources are present in the culture medium (catabolic repression). Crc appears to be a component of a signal transduction pathway modulating carbon metabolism in pseudomonads, although its mode of action is unknown. To better understand the role of Crc, the proteome profile of two otherwise isogenic P. putida strains containing either a wild-type or an inactivated crc allele was compared. The results showed that Crc is involved in the catabolic repression of the hpd and hmgA genes from the homogentisate pathway, one of the central catabolic pathways for aromatic compounds that is used to assimilate intermediates derived from the oxidation of phenylalanine, tyrosine, and several aromatic hydrocarbons. This led us to analyze whether Crc also regulates the expression of the other central catabolic pathways for aromatic compounds present in P. putida. It was found that genes required to assimilate benzoate through the catechol pathway (benA and catBCA) and 4-OH-benzoate through the protocatechuate pathway (pobA and pcaHG) are also negatively modulated by Crc. However, the pathway for phenylacetate appeared to be unaffected by Crc. These results expand the influence of Crc to pathways used to assimilate several aromatic compounds, which highlights its importance as a master regulator of carbon metabolism in P. putida.

Elastic image registration of 2‐D gels for differential and repeatability studies

“…We used the same numbers as in the original paper to label the 13 spots identified in ref. [10]. As can be seen, all 13 proteins can be properly and easily identified in our registration.…”

“…We conclude that every protein with differential expression patterns that was identified in ref. [10] has been correctly picked out by our algorithm, too. We also picked out additional proteins that, according to our registration method, exhibit a differential expression pattern.…”

“…Among others, the results showed that Crc is involved in the catabolic repression of hpd and hmgA genes from the homogentisate pathway, one of the central catabolic pathways for aromatic compounds. Based on four gels, a change in the expression of 13 proteins of the metabolic pathway was identified [10]. We registered the same gels and checked our results against those of [10].…”

“…Based on four gels, a change in the expression of 13 proteins of the metabolic pathway was identified [10]. We registered the same gels and checked our results against those of [10]. We show in Fig.…”

“…Those, however, were not selected in ref. [10] because they were unrelated to the metabolic pathway under study.…”