PHAGE DISPLAY SELECTION OF PEPTIDES AGAINST ENZYME-I OF THE PHOSPHOENOLPYRUVATE-SUGAR PHOSPHOTRANSFERASE SYSTEM (PTS)

The bacterial phosphoenolpyruvate-sugar phosphotransferase system (PTS ) mediates the uptake and phosphorylation of carbohydrates and is invo lved in. signal transduction. In response to the availability of carbo hydrates it modulates catabolite repression, intermediate metabolism, gene expression and chemotaxis. It is ubiquitous in bacteria but does not occur in animals and plants. Uniqueness and pleiotropic function m ake the PTS a target for new antibacterial drugs. Enzyme I is the firs t component of the divergent protein phosphorylation cascade of the PT S. It transfers phosphoryl groups from phosphoenolpyruvate to the gene ral phosphoryl carrier protein HPr. Six 15-mer, nine 10-mer and nine B -mer peptides that inhibit enzyme I were selected from phage display l ibraries. Of these, 16 were synthesized and characterized. The majorit y of the peptides contain a histidine with an adjacent arginine. Two p eptides were found to contain cysteines but no histidine. All peptides are rich in basic residues and lack acidic amino acids. The peptides inhibit the phosphotransferase system in vitro with IC50 of between 10 mu M and 2 mM. Some, but not all, of the peptides inhibit cell growth in the agar diffusion test by an as yet undefined mechanism. All pept ides are phosphorylated by enzyme I, and some are regenerated by slow autocatalytic hydrolysis of the phospho-peptide bond.