Antibiotic resistance in Staphylococcus aureus by allosteric control of Penicillin-Binding Protein 2a

OTERO, LISANDRO HORACIO; FISHOVITZ, JENNIFER; ROJAS-ALTUVE, ALZORAY; CHANG, MAYLAND; MOBASHERY, SHAHRIAR; HERMOSO, JUAN ANTONIO

Rosario

Congreso; L Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2014

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

The expression of penicillin-binding protein 2a (PBP2a) is the basis for the broad clinical resistance to β-lactam antibiotics by methicillin-resistant Staphylococcus aureus (MRSA). The high-molecular mass penicillin-binding proteins of bacteria catalyze the transglycosylase and transpeptidase activities required for the biosynthesis of the peptidoglycan polymer that comprises the major constituent of the bacterial cell wall. In bacteria susceptible to β-lactam antibiotics, the transpeptidase activity of their penicillin-binding proteins (PBPs) is lost as a result of irreversible acylation of an active-site serine by the β-lactam antibiotics. In contrast, the PBP2a of MRSA is resistant to β-lactam acylation and successfully catalyzes the DD-transpeptidation reaction necessary to complete the cell wall. We report herein the identification of an allosteric domain of PBP2a - a remarkable 60 Å distant from the DD-transpeptidase active site - by X-ray crystallography and kinetic studies. When this allosteric site is occupied, a multiresidue conformational change culminates in the opening of the active site to permit substrate entry. The ability of an anti-MRSA β-lactam antibiotic to stimulate allosteric opening of the active site, thus predisposing PBP2a to inactivation by a second β-lactam molecule, opens an unprecedented realm for β-lactam antibiotic structure-based design.