Inhibitor Design and Modeling of Antibiotic Resistance Enzymes

Research Summary
This proposal describes a collaborative research effort to design inhibitors of two amino glycoside 3'-phosphotransferase enzymes (APH(3'}-IIIa and APH(3')-II). These enzymes are involved in the ATP- dependent phosphorylation of amino glycoside antibiotics. The phosphorylation of amino glycosides compromises their ability to kill various strains of pathogenic bacteria and limits their clinical relevance. Bacterial resistance to amino glycoside antibiotics is one important example of the role that covalent modification of antibiotics plays in the current crisis of antibiotic resistance. Inhibitors of amino glycoside- modifying enzymes may make an important contribution to once again establishing the clinical effectiveness of this important class of antibiotics.

A key contact in the active site Of APH(3'}-IIIa is a π - π stacking interaction between Tyr42 and the adenine ringof bound nucleotides. Since the aromatic ring of Tyr42 is conserved among most of the APH(3') enzymes, this type of π - π interaction may be involved in the recognition of the adenine ring throughout this important family of antibiotic-modifying enzymes. the research in this proposal involves a strategy to exploit the stacking interaction to design inhibitors of APH(3')-IIIa and APH(3'}-II. A large number of compounds will be tested as competitive inhibitors of these enzymes to establish the characteristics of these systems that can bind in the adenine binding regions of these two enzymes. This molecular screening will yield a template structure that can be further modified after docking studies with the two phosphotransferase enzymes. It is believed that these second generation compounds will be potent inhibitors of the APH(3') family of enzymes