Evaluation of the type I signal peptidase as antibacterial target for biofilm-associated infections of Staphylococcus epidermidis

Abstract

The development of antibacterial resistance is inevitable and is a major concern in hospitals and communities. Moreover, biofilm-grown bacteria are less sensitive to antimicrobial treatment. In this respect, the Gram-positiveStaphylococcus epidermidisis an important source of nosocomial biofilm-associated infections. In the search for new antibacterial therapies, the type I signal peptidase (SPase I) serves as a potential target for development of antibacterials with a novel mode of action. This enzyme cleaves off the signal peptide from secreted proteins, making it essential for protein secretion, and hence for bacterial cell viability.S. epidermidisencodes three putative SPases I (denoted Sip1, Sip2 and Sip3), of which Sip1 lacks the catalytic lysine. In this report, we investigated the activeS. epidermidisSPases I in more detail. Sip2 and Sip3 were found to complement a temperature-sensitiveEscherichia coli lepBmutant, demonstrating theirin vivofunctional activity.In vitrofunctional activity of purified Sip2 and Sip3 proteins and inhibition of their activity by the SPase I inhibitor arylomycin A2were further illustrated using a fluorescence resonance energy transfer (FRET)-based assay. Furthermore, we demonstrated that SPase I not only is an attractive target for development of novel antibacterials against free-living bacteria, but also is a feasible target for biofilm-associated infections.