Design and evaluation of pilicides: potential novel antibacterial agents directed against uropathogenic Escherichia coli.

KEYWORDS: antibiotics´bioorganic chemistry´chaperone proteins´peptidomimetics The heavy use of antibiotics during the second half of the last century has resulted in widespread bacterial resistance. Overcoming resistance requires the development of antibiotics aimed at new targets in microorganisms. Preferably, such targets should be highly conserved in bacteria and required for pathogenesis, but not found in humans. Herein, we describe the design of a class of potential novel antibacterial agents called ªpilicidesº. Pilicides target periplasmic chaperones, that is proteins required for the assembly of organelles (pili) that allow pathogenic Gram negative bacteria to adhere to host tissue. Synthetic routes that enable the combinatorial synthesis of two families of pilicides have been developed and used to prepare an initial set of eight pilicides. Surface plasmon resonance showed that the pilicides bind to two bacterial chaperones from uropathogenic Escherichia coli and that the binding was in agreement with affinities predicted by calculations. Importantly, the most potent compounds were able to dissociate chaperone ± pilus protein complexes which are required for the assembly of pili. A large number of infectious Gram negative bacteria produce pili, which are a family of extracellular, supramolecular protein organelles that mediate attachment to host tissue. E. coli is the main cause of urinary tract infections and the bacterium assembles two types of disease-associated pili. Type 1 pili are important for the development of common urinary tract infections affecting the bladder (cystitis), while P pili are expressed in more severe infections that lead to kidney damage (pyelonephritis). Type 1 and P pili have the saccharide-binding adhesins FimH and PapG, respectively, located at the tip of the rodlike pilus, which is composed of approximately 1000 pilus proteins of a few different types. These two complex organelles are assembled by the molecular chaperones FimC and PapD, respectively. The chaperones bind to the pilus proteins as they cross the cytoplasmic membrane and bring them across the periplasmic space to assembly sites at the outer membrane of the bacterium. Formation of chaperone ± pilus protein complexes is required for assembly of pili, without which coloniza-tion of host tissue can not occur. Bacterial periplasmic chaperones therefore appear to be ideal targets for the development of novel antibacterial agents. Synthetic peptides from the conserved C-termini of pilus proteins are bound by the PapD chaperone, [7] and the structures of complexes between PapD and two of these peptides have been solved by X-ray crystallography. The structure of the complex …