A microtiter plate-based beta-lactam binding assay for inhibitors of high-molecular-mass penicillin-binding proteins.

High-molecular-mass penicillin-binding proteins (HMM PBPs) are essential for bacterial cell wall biosynthesis and are the lethal targets of beta-lactam antibiotics. When purified, HMM PBPs give undetectable or weak enzyme activity. This has impeded efforts to develop assays for HMM PBPs and to develop new inhibitors for HMM PBPs as HMM PBP targeted antibacterial agents. However, even when purified, HMM PBPs retain their ability to bind beta-lactams. Here we describe a fluorescently detected microtiter plate-based assay for inhibitor binding to HMM PBPs based on competition with biotin-ampicillin conjugate (BIO-AMP) binding.