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Phage display-derived inhibitor of the essential cell wall biosynthesis enzyme MurF.

ABSTRACT: BACKGROUND: To develop antibacterial agents having novel modes of action against bacterial cell wall biosynthesis, we targeted the essential MurF enzyme of the antibiotic resistant pathogen Pseudomonas aeruginosa. MurF catalyzes the formation of a peptide bond between D-Alanyl-D-Alanine (D-Ala-D-Ala) and the cell wall precursor uridine 5'-diphosphoryl N-acetylmuramoyl-L-alanyl-D-glutamyl-meso-diaminopimelic acid (UDP-MurNAc-Ala-Glu-meso-A2pm) with the concomitant hydrolysis of ATP to ADP and inorganic phosphate, yielding UDP-N-acetylmuramyl-pentapeptide. As MurF acts on a dipeptide, we exploited a phage display approach to identify peptide ligands having high binding affinities for the enzyme. RESULTS: Screening of a phage display 12-mer library using purified P. aeruginosa MurF yielded to the identification of the MurFp1 peptide. The MurF substrate UDP-MurNAc-Ala-Glumeso-A2pm was synthesized and used to develop a sensitive spectrophotometric assay to quantify MurF kinetics and inhibition. MurFp1 acted as a weak, time-dependent inhibitor of MurF activity but was a potent inhibitor when MurF was pre-incubated with UDP-MurNAc-Ala-Glu-meso-A2pm or ATP. In contrast, adding the substrate D-Ala-D-Ala during the pre-incubation nullified the inhibition. The IC50 value of MurFp1 was evaluated at 250 microM, and the Ki was established at 420 microM with respect to the mixed type of inhibition against D-Ala-D-Ala. CONCLUSION: MurFp1 exerts its inhibitory action by interfering with the utilization of D-Ala-D-Ala by the MurF amide ligase enzyme. We propose that MurFp1 exploits UDP-MurNAc-Ala-Glu-meso-A2pm-induced structural changes for better interaction with the enzyme. We present the first peptide inhibitor of MurF, an enzyme that should be exploited as a target for antimicrobial drug development.

SUBMITTER: Paradis-Bleau C

PROVIDER: S-EPMC2626591 | biostudies-literature | 2008

REPOSITORIES: biostudies-literature

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Phage display-derived inhibitor of the essential cell wall biosynthesis enzyme MurF.

Paradis-Bleau Catherine C Lloyd Adrian A Sanschagrin François F Clarke Tom T Blewett Ann A Bugg Timothy D H TD Levesque Roger C RC

BMC biochemistry 20081219

<h4>Background</h4>To develop antibacterial agents having novel modes of action against bacterial cell wall biosynthesis, we targeted the essential MurF enzyme of the antibiotic resistant pathogen Pseudomonas aeruginosa. MurF catalyzes the formation of a peptide bond between D-Alanyl-D-Alanine (D-Ala-D-Ala) and the cell wall precursor uridine 5'-diphosphoryl N-acetylmuramoyl-L-alanyl-D-glutamyl-meso-diaminopimelic acid (UDP-MurNAc-Ala-Glu-meso-A2pm) with the concomitant hydrolysis of ATP to ADP ...[more]

PMID: 19099588

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Project description:PURPOSE:Osteosarcoma represents the most common malignant primary bone tumor in childhood; however, the survival rate has remained unchanged for the past 20 years. To improve existing diagnosis and treatment methods and broaden the spectrum of imaging agents that can be used for early detection and assessment of tumor response to therapy, we performed a phage display-based screening for peptide sequences that bind specifically to osteosarcoma cells. EXPERIMENTAL DESIGN:From the Ph.D.-12 phage display peptide library composed of 2.7 x 10(9) different displayed peptides, one peptide was enriched after four rounds of in vitro selection in 143B osteosarcoma tumor cells with 293T human embryonic kidney cells as a control. Both the peptide and the phage clone displaying the peptide were conjugated with fluorescent dyes for in vitro cell and ex vivo tumor tissue stainings. The peptide was further labeled with (18)F for positron emission tomography imaging studies. Cell uptake and efflux and ex vivo biodistribution were also done with (18)F-labeled osteosarcoma specific peptide. RESULTS:ASGALSPSRLDT was the dominant sequence isolated from biopanning and named as OSP-1. OSP-1 shares a significant homology with heparinase II/III family protein, which binds and reacts with heparan sulfate proteoglycans. The fluorescence staining showed that FITC-OSP-1-phage or Cy5.5-OSP-1 had high binding with a panel of osteosarcoma cell lines, much less binding with UM-SCC1 human head and neck squamous cell carcinoma cells, and almost no binding with 293T cells, whereas the scrambled peptide OSP-S had virtually no binding to all the cell lines. (18)F-OSP-1 had significantly higher accumulation in 143B tumor cells both in vitro and in vivo than (18)F-OSP-S. (18)F-OSP-1 also had higher uptake in 143B tumors than in UM-SCC-1 tumors. CONCLUSIONS:Our data suggest that OSP-1 peptide is osteosarcoma specific, and the binding site of OSP-1 might be related to heparan sulfate proteoglycans. Appropriately labeled OSP-1 peptide has the potential to serve as a novel probe for osteosarcoma imaging.

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Phage display-derived inhibitor of the essential cell wall biosynthesis enzyme MurF.

Publications

Phage display-derived inhibitor of the essential cell wall biosynthesis enzyme MurF.

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