The expression of the genes involved in leucine catabolism of Pseudomonas aeruginosa is controlled by the transcriptional regulator LiuR and by the CbrAB/Crc system |
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Authors: | Alma Laura Díaz-Pérez Cinthia Núñez Victor Meza Carmen Jesús Campos-García |
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Affiliation: | 1. Laboratorio de Biotecnología Microbiana, Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, 58030, Mexico;2. Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos, 62210, Mexico;3. Laboratorio de Diferenciación Celular, Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, 58030, Mexico |
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Abstract: | Pseudomonas aeruginosa metabolizes leucine through the leucine/isovalerate utilization pathway, whose enzymes are encoded in the liuRABCDE gene cluster (liu). In this study, we investigated the role of the LiuR protein in the liu cluster regulation. Our results indicated that liu expression is regulated at the transcriptional level by LiuR. Mobility shift assays using purified recombinant His-tagged LiuR showed that it was able to bind at the promoter region of liuR, in a dose-dependent manner. Results revealed that expression of the liu operon is subjected to carbon catabolite repression control (CCR); protein LiuD was strongly expressed in the presence of leucine, but it was repressed in the presence of glucose or succinate. Furthermore, this CCR control was dependent on LiuR as in the liuR- mutant the LiuD protein was strongly expressed in all the carbon sources tested. In agreement with this result, in the absence of the Crc protein, LiuD was expressed independently of the carbon source used, whereas in a cbrB- mutant its expression was severely impaired. The results indicated that the liu cluster is subjected to a coordinated transcriptional and translational regulation by the LiuR repressor and by the CbrAB/Crc system, respectively, in response to the available carbon source. |
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Keywords: | Leucine catabolism Acyclic terpenes Catabolite repression Transcriptional regulation Corresponding author. Laboratorio de Biotecnología Microbiana, Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Edif. B-3, Ciudad Universitaria, CP 58030, Morelia, Michoacán, Mexico. Fax: +52 4433265788. |
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