In our recent article published in Nature Communications entitled: “Shared structural mechanisms of alternating access between the secondary peptide transporter SbmA and ABC transporters” we used pulsed Dipolar EPR Spectroscopy (PDS), PELDOR/DEER to show the antimicrobial peptide membrane transporter SbmA is energized by the proton gradient, and is structurally related to ABC transporters. SbmA therefore bridges the structural divide between primary and secondary transporters. Here, we determine the structures of SbmA by cryoEM in occluded and inward-facing states. In contrast to ABC transporters, where nucleotide binding, hydrolysis and release steer conformational changes necessary for substrate translocation, PELDOR/DEER spectroscopy reveals the complete conformational ensemble of SbmA and shows how pH changes induce conformational transitions, consistent with a mechanism of substrate internalization that utilizes the transmembrane proton gradient. More information could be found here.
