Effect of vfr mutation on global gene expression and catabolite repression control of Pseudomonas aeruginosa

Abstract

Vfr of Pseudomonas aeruginosa is 91 % similar to the cAMP receptor protein (CRP) of Escherichia coli. Based on the high degree of sequence homology between the two proteins, the question arose whether Vfr had a global regulatory effect on gene expression for P. aeruginosa as CRP did for E. coli. This report provides two-dimensional polyacrylamide gel electrophoretic evidence that Vfr is a global regulator of gene expression in P. aeruginosa. In a vfr101 ::aacC1 null mutant, at least 43 protein spots were absent or decreased when compared to the proteome pattern of the parent strain. In contrast, 17 protein spots were absent or decreased in the parent strain when compared to the vfr101 ::aacC1 mutant. Thus, a mutation in vfr affected production of at least 60 proteins in P. aeruginosa. In addition, the question whether Vfr and CRP shared similar mechanistic characteristics was addressed. To ascertain whether Vfr, like CRP, can bind cAMP, Vfr and CRP were purified to homogeneity and their apparent dissociation constants (K d ) for binding to cAMP were determined. The K d values were 16 µM for Vfr and 04 µM for CRP, suggesting that these proteins have a similar affinity for cAMP. Previously the authors had demonstrated that Vfr could complement a crp mutation and modulate catabolite repression in E. coli. This study presents evidence that Vfr binds to the E. coli lac promoter and that this binding requires the presence of cAMP. Finally, the possible involvement of Vfr in catabolite repression control in P. aeruginosa was investigated. It was found that succinate repressed production of mannitol dehydrogenase, glucose-6-phosphate dehydrogenase, amidase and urocanase both in the parent and in two vfr null mutants. This implied that catabolite repression control was not affected by the vfr null mutation. In support of this, the cloned vfr gene failed to complement a mutation in the P. aeruginosa crc gene. Thus, although Vfr is structurally similar to CRP, and is a global regulator of gene expression in P. aeruginosa, Vfr is not required for catabolite repression control in this bacterium.

Anaerobic Catabolism of Aromatic Compounds: a Genetic and Genomic View

“…The repression of catabolic pathways frequently results from the integration of several signals rather than just from the presence of a preferred compound in the medium. Although a protein with high similarity to E. coli CRP is encoded in the chromosome of several Pseudomonas strains, this protein does not seem to mediate catabolite repression (249,306,348). On the contrary, some other proteins such as Crc (catabolite repression control) (249,254,306), PtsN and PtsO (nitrogen phosphotransferase transport system) (233,281), some o-type terminal oxidases (CyoB) that sense the redox state of the cell (250,280), and the BphQ response regulator (264) have been reported to be involved in the catabolite repression of several aromatic degradation pathways in nonenteric bacteria.…”

Role of fimV in type II secretion system-dependent protein secretion of Pseudomonas aeruginosa on solid medium

“…The former gene encodes a well-known global regulator that controls several processes (expression of genes encoding proteases, exotoxin A, twitching motility and QS) (Albus et al, 1997;Beatson et al, 2002;Suh et al, 2002;Kanack et al, 2006;Fox et al, 2008) and the latter encodes a protein involved in type IV pili assembly but has been poorly studied so far (Semmler et al, 2000;Ahn et al, 2004). Both genes were also reported to be required for twitching motility and indeed, as expected, we observed that the selected mutants were impaired for this movement mode (data not shown).…”

Dual Involvement of CbrAB and NtrBC in the Regulation of Histidine Utilization inPseudomonas fluorescensSBW25

“…1 In nonenteric Gram-negative bacteria, such as Pseudomonas, general induction of hut expression is not well understood. Succinate-induced catabolite repression (based solely on enzyme activity assays) has been reported (Hug et al 1968;Phillips and Mulfinger 1981), although no role has been found for the global regulatory proteins Crc (catabolic repression control; Hester et al 2000) and Vfr (virulence factor regulator, which is homologous to the E. coli CAP protein; Suh et al 2002). Recent work has shown the involvement of a newly discovered two-component regulatory system, CbrAB (Nishijyo et al 2001;Zhang and Rainey 2007).…”