Interactions between penicillin-binding proteins (PBPs) and two novel classes of PBP inhibitors, arylalkylidene rhodanines and arylalkylidene iminothiazolidin-4-ones

Structure−Activity Relationships of Phenyl-Furanyl-Rhodanines as Inhibitors of RNA Polymerase with Antibacterial Activity on Biofilms

The dramatic rise of antibiotic-resistant bacteria over the past two decades has stressed the need for completely novel classes of antibacterial agents. Accordingly, recent advances in the study of prokaryotic transcription open new opportunities for such molecules. This paper reports the structure-activity relationships of a series of phenyl-furanyl-rhodanines (PFRs) as antibacterial inhibitors of RNA polymerase (RNAP). The molecules have been evaluated for their ability to inhibit transcription and affect growth of bacteria living in suspension or in a biofilm and for their propensity to interact with serum albumin, a critical parameter for antibacterial drug discovery. The most active of these molecules inhibit Escherichia coli RNAP transcription at concentrations of </=10 microM and have promising activities against various Gram-positive pathogens including Staphylococcus epidermidis biofilms, a major cause of nosocomial infection.

Penicillin binding proteins: key players in bacterial cell cycle and drug resistance processes

Bacterial cell division and daughter cell formation are complex mechanisms whose details are orchestrated by at least a dozen different proteins. Penicillin-binding proteins (PBPs), membrane-associated macromolecules which play key roles in the cell wall synthesis process, have been exploited for over 70 years as the targets of the highly successful beta-lactam antibiotics. The increasing incidence of beta-lactam resistant microorganisms, coupled to progress made in genomics, genetics and immunofluorescence microscopy techniques, have encouraged the intensive study of PBPs from a variety of bacterial species. In addition, the recent publication of high-resolution structures of PBPs from pathogenic organisms have shed light on the complex intertwining of drug resistance and cell division processes. In this review, we discuss structural, functional and biological features of such enzymes which, albeit having initially been identified several decades ago, are now being aggressively pursued as highly attractive targets for the development of novel antibiotherapies.

One-pot synthesis of 5-arylidene-2-imino-4-thiazolidinones under microwave irradiation

A rapid and easy solvent free one-pot synthesis of 5-arylidene-2-imino-4-thiazolidinones by condensation of the thioureas with chloroacetic acid and an aldehyde under microwave-irradiation is described.

Beta-lactam antibiotic resistance: a current structural perspective

Bacterial resistance to beta-lactam antibiotics can be achieved by any of three strategies: the production of beta-lactam-hydrolyzing beta-lactamase enzymes, the utilization of beta-lactam-insensitive cell wall transpeptidases, and the active expulsion of beta-lactam molecules from Gram-negative cells by way of efflux pumps. In recent years, structural biology has contributed significantly to the understanding of these processes and should prove invaluable in the design of drugs to combat beta-lactam resistance in the future.

Novel synthetic molecules targeting the bacterial RNA polymerase assembly

OBJECTIVES

Despite extensive functional screening of the bacterial RNA polymerase (RNAP) over the past years, very few novel inhibitors have been reported. We have, therefore, decided to screen with a radically different, non-enzymic, protein-protein interaction assay. Our target is the highly conserved RNAP-sigma interaction that is essential for transcription.

METHODS

Small molecule inhibitors of the RNAP-sigma interaction were tested for their activity on transcription and on bacteria.

RESULTS

These compounds have antibacterial activity against Gram-positive bacteria including multiresistant clinical isolates.

CONCLUSIONS

This is, to our knowledge, the first example of a small molecule inhibitor of this interaction.

Does the cell wall of bacteria remain a viable source of targets for novel antibiotics?

Whether the bacterial cell wall remains a viable source of novel antibacterials is addressed here by reviewing screen and design strategies for discovery of antibacterials with a focus on their output. Inhibitors for which antibacterial activity has been shown to be due to specific inhibition of a reaction (antibacterially validated inhibitors) are known for 8 of the 14 conserved essential steps of the pathway. Antibacterially validated enzyme inhibitors exist for six of these steps. The possible obstacles to finding validated inhibitors of the remaining enzymes are discussed and some strategies are suggested.