Permeation through the Cell Membrane of a Boron-Based β-Lactamase Inhibitor

Bacteria express beta-lactamases to counteract the beneficial action of antibiotics. Benzo[b]-thiophene-2-boronic acid (BZB) derivatives are beta-lactamase inhibitors and, as such, promising compounds to be associated with beta-lactam antibacterial therapies. The uncharged form of BZB, in particular, is suggested to diffuse through the outer membrane of Gram negative bacteria. In this study, through the combination of electrophysiological experiments across reconstituted PC/n-decane bilayers and metadynamics-based free energy calculations, we investigate the permeation mechanism of boronic compounds. Our experimental data establish that BZB passes through the membrane, while computer simulations provide hints for the existence of an aqueous, water-filled monomolecular channel. These findings provide new perspectives for the design of boronic acid derivatives with high membrane permeability.