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An ampD gene in Pseudomonas aeruginosa encodes a negative regulator of AmpC beta-lactamase expression.

ABSTRACT: The ampD and ampE genes of Pseudomonas aeruginosa PAO1 were cloned and characterized. These genes are transcribed in the same orientation and form an operon. The deduced polypeptide of P. aeruginosa ampD exhibited more than 60% similarity to the AmpD proteins of enterobacteria and Haemophilus influenzae. The ampD product transcomplemented Escherichia coli ampD mutants to wild-type beta-lactamase expression.

SUBMITTER: Langaee TY

PROVIDER: S-EPMC106040 | biostudies-literature | 1998 Dec

REPOSITORIES: biostudies-literature

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An ampD gene in Pseudomonas aeruginosa encodes a negative regulator of AmpC beta-lactamase expression.

Langaee T Y TY Dargis M M Huletsky A A

Antimicrobial agents and chemotherapy 19981201 12

The ampD and ampE genes of Pseudomonas aeruginosa PAO1 were cloned and characterized. These genes are transcribed in the same orientation and form an operon. The deduced polypeptide of P. aeruginosa ampD exhibited more than 60% similarity to the AmpD proteins of enterobacteria and Haemophilus influenzae. The ampD product transcomplemented Escherichia coli ampD mutants to wild-type beta-lactamase expression. ...[more]

PMID: 9835532

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Project description:In Enterobacteriaceae, the transcriptional regulator AmpR, a member of the LysR family, regulates the expression of a chromosomal β-lactamase AmpC. The regulatory repertoire of AmpR is broader in Pseudomonas aeruginosa, an opportunistic pathogen responsible for numerous acute and chronic infections including cystic fibrosis. In addition to regulating ampC, P. aeruginosa AmpR regulates the sigma factor AlgT/U and production of some quorum sensing (QS)-regulated virulence factors. In order to better understand the ampR regulon, we compared the transcriptional profile generated using DNA microarrays of the prototypic P. aeruginosa PAO1 strain with its isogenic ampR deletion mutant, PAOΔampR. Transcriptome analysis demonstrates that the AmpR regulon is much more extensive than previously thought, with the deletion of ampR influencing the differential expression of over 500 genes. In addition to regulating resistance to β-lactam antibiotics via AmpC, AmpR also regulates non-β-lactam antibiotic resistance by modulating the MexEF-OprN efflux pump. Other virulence mechanisms including biofilm formation and QS-regulated acute virulence factors are AmpR-regulated. Real-time PCR and phenotypic assays confirmed the microarray data. Further, using a Caenorhabditis elegans model, we demonstrate that a functional AmpR is required for P. aeruginosa pathogenicity. AmpR, a member of the core genome, also regulates genes in the regions of genome plasticity that are acquired by horizontal gene transfer. Further, we show differential regulation of other transcriptional regulators and sigma factors by AmpR, accounting for the extensive AmpR regulon. The data demonstrates that AmpR functions as a global regulator in P. aeruginosa and is a positive regulator of acute virulence while negatively regulating biofilm formation, a chronic infection phenotype. Unraveling this complex regulatory circuit will provide a better understanding of the bacterial response to antibiotics and how the organism coordinately regulates a myriad of virulence factors in response to antibiotic exposure.

Project description:AmpC is a group I, class C -lactamase present in most Enterobacteriaceae and in Pseudomonas aeruginosa and other nonfermenting gram-negative bacilli. The β-lactam class of antibiotics is one of the most important structural classes of antibacterial compounds and act by inhibiting the bacterial D ,D - transpeptidases that are responsible for the final step of peptidoglycan cross-linking. Our main aim in the study is to screen possible inhibitors against AmpC / β - lactamase (an enzyme responsible for antimicrobial activity in Pseudomonas aeruginosa), through virtual screening of 1364 NCI (National Cancer Institute) diversity set II compounds. Homology Model of AmpC / β - lactamase was constructed using MODELLER and the Model was validated using PROCHECK and Verify 3D programs to obtain a stable structure, which was further used for virtual screening of NCI (National Cancer Institute) diversity set II compounds through molecular Docking studies using Autodock. The amino acid sequence of the β - lactamase was also subjected to ScanProsite web server to find any pattern present in the sequence. After the prediction of 3-dimensional model of AmpC/ β-lactamase, the possible Active sites ofβ - lactamase were determined using LIGSITE(csc) and CastP web servers simultaneously. The Docked complexes were validated and Enumerated based on the Autodock Scoring function to pick out the best inhibitor based on Autodock energy score. Thus from the entire 1364 NCI diversity set II compounds which were Docked, the best four docking solutions were selected (ZINC12670903, ZINC17465965, ZINC11681166 and ZINC13099024). Further the Complexes were analyzed through LIGPLOT for their interaction for the 4 best docked NCI diversity set II compounds. Thus from the Complex scoring and binding ability it is deciphered that these NCI diversity set II compounds could be promising inhibitors for Pseudomonas aeruginosa using AmpC /β - lactamase as Drug target yet pharmacological studies have to confirm it.

Dataset Information

An ampD gene in Pseudomonas aeruginosa encodes a negative regulator of AmpC beta-lactamase expression.

Publications

An ampD gene in Pseudomonas aeruginosa encodes a negative regulator of AmpC beta-lactamase expression.

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