Lipid-dependent conformational dynamics of bacterial ATP-binding cassette transporter Sav1866.

Sav1866, a bacterial ATP-binding cassette (ABC) exporter, plays a crucial role in cellular processes by facilitating the efflux of a diverse range of substrates, including drugs, chemotherapeutic agents, peptides, and lipids. This efflux activity significantly impacts the effectiveness of various therapies against bacterial infections. In our recent investigation, we focused on understanding the conformational dynamics of Sav1866 within different lipid environments. Specifically, we explored its behavior in environments composed of DMPC and POPE lipids, which exhibit crucial distinctions not only in their headgroup polarity but also in the length and saturation of their hydrophobic tails. Our extensive set of equilibrium microsecond-level all-atom molecular dynamics (MD) simulations revealed significant distinctions in transporter behavior influenced by these lipid compositions. We observed a rapid transition to an occluded-inward-facing (IF-occ) conformation in POPE environments, contrasting with a channel-like behavior in DMPC environments, deviating from the expected alternating access mechanism (AAM). These findings underscore the significant impact of lipid compositions on ABC transporter function, offering new perspectives on membrane transport mechanisms.