The Pseudomonas putida Crc global regulator is an RNA binding protein that inhibits translation of the AIkS transcriptional regulator

• Published in: Molecular microbiology Vol. 64; no. 3; p. 665
• Main Authors: Moreno, Renata, Ruiz-Manzano, Ana, Yuste, Luis, Rojo, Fernando
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.05.2007
• Subjects: Bacteria; Bacteriology; Gene expression; Genes; Proteins; Ribonucleic acid; RNA
• ISSN: 0950-382X; 1365-2958

The Crc protein is a global regulator that controls the hierarchical assimilation of carbon sources in Pseudomonads by inhibiting expression of several catabolic pathways. Crc does not bind DNA and its mechanism of action has remained elusive. Among other genes, Crc inhibits expression of a1kS, the transcriptional activator of the Pseudomonas putida OCT plasmid alkane degradation pathway. A1kS activates expression of its own gene. In the presence of saturating A1kS levels, translational fusions of a1kS to the lacZ reporter gene were responsive to Crc, but transcriptional fusions were not. In translational fusions, the first 33 nt of a1kS mRNA, which includes up to position +3 relative to the translation start site, were sufficient to confer an efficient response to Crc. In vitro, purified Crc could bind specifically to an a1kS mRNA fragment spanning positions +1 to +43, comprising the translation initiation region. We have previously shown that Crc has little effect on the stability of a1kS mRNA. We conclude that Crc modulates A1kS levels by binding to the translation initiation region of a1kS mRNA, thereby inhibiting translation. Because A1kS is an unstable protein present in limiting amounts, reducing its levels leads to decreased expression of all genes in the pathway. [PUBLICATION ABSTRACT]