Fur (ferric uptake regulation) protein and CAP (catabolite‐activator protein) modulate transcription of fur gene in Escherichia coli

Abstract

A fusion between the fur (ferric uptake regulation) gene, known to mediate negative regulation of iron absorption in Escherichia coli, and lacZ was constructed in vitro. P-Galactosidase levels of cells harboring this fusion were under the control of sequences contained in a 185-bp DNA fragment located upstream of the fur structural gene. The fusion was prepared in multicopy (pVLN102 plasmid) and low-copy-number states, the latter constructed as a I phage lysogen carrying a fur'-'lacZ insert. DNase I footprinting experiments with purified Fur protein, performed on a 250-bp restriction fragment carrying the promoter region of the fusion, showed the presence of a single Fur-protected site overlapping the -10 region of a potential promoter sequence. Examination of the DNA sequences located upstream of the fur gene revealed a possible binding site for the catabolite-activator protein (CAP). P-Galactosidase synthesis of E. coli cells harboring the fusion were measured in fur, crp and cya genetic backgrounds and compared with the corresponding levels in wild-type strains. The data obtained indicate a moderate autoregulation of fur expression by its gene product and also a significant stimulation by the CAMP-CAP system. Transcription start sites were mapped by primer-extension experiments with total RNA obtained in vivo from cells harboring pVLN102. The results show that transcription of thefur gene is initiated from at least two different sites separated by 6 bp, which appear to originate from two overlapping promoters sensitive to catabolic activation.

Cloning and Characterization of the fur Gene from Moraxella bovis

“…2). A CAP-binding site sequence could be also identified in the upstream regions of E. coli and Y. pestis fur genes (19,27). M. bovis-fur-gene expression, like E. coli, may also be regulated through the cAMP-CAP system (19).…”

“…De Lorenzo et al have indicated that the E. coli fur gene is auto-regulated by its own fur box, with a decrease of fur expression when cells are grown under iron-sufficient conditions (19). To examine whether iron conditions alter the fur expression levels, cell extracts of bacteria grown under iron-sufficient and iron-deficient conditions were analyzed by western blotting with the anti-M. bovis Fur antiserum (Fig.…”

Identification, isolation, and analysis of a gene cluster involved in iron acquisition by Pseudomonas mendocina ymp

“…4) (de Lorenzo et al 1987;Ochsner and Vasil 1996). Though Fur is not auto-regulated in P. aeruginosa, it is apparently preceded by a fur box in P. mendocina and E. coli (de Lorenzo et al 1988;Ochsner et al 1999). …”

Global Regulatory Pathways and Cross-talk ControlPseudomonas aeruginosaEnvironmental Lifestyle and Virulence Phenotype

“…Cyclic AMP is involved in regulating gene expression in many bacterial species in response to environmental cues (De Lorenzo, 1988;Botsford, 1992;Macfadyen, 1998) and is produced by the enzymatic activity of adenylate cyclase (AC) enzymes. The P. aeruginosa PAO1 genome encodes three ACs, the intracellular ACs, CyaA and CyaB, and a secreted effector ExoY (Stover, 2000;Wolfgang, 2003b).…”