Fig. 4: BceS exhibits a high degree of intrinsic flexibility.
From: Architecture of a complete Bce-type antimicrobial peptide resistance module
a 2D class-averages of detergent solubilized BceAB-S. Individual TM helices for BceS are present in the interior of the detergent micelle, while the cytoplasmic domains of BceS are often fuzzy. Purple asterisks indicate the BceS cytosolic domains in 2D averages where these domains exhibit a very large degree of structural heterogeneity. b The first three principal components of motion in the BceS cytosolic domains identified from 3DVA in cryoSPARC. The top and bottom rows indicate the extreme extent of motion observed in principal component. In each panel BceS is colored and BceAB and the detergent micelle are shown in grey. Red arrows indicate the direction of BceS motions observed. c Individual classes obtained from 3D classification of BceAB-S particles. All classes are oriented with the detergent micelle and BceAB transporter in the same position to highlight the variety of conformations that BceS can adopt within the complex. d View of the atomic model of BceS monomers fit into the local resolution filtered cryo-EM map of nucleotide-free BceAB-S. Near-atomic resolutions are obtained in the TM and HAMP domains, while the resolution steeply decreases entering the cytosolic DHp and CA domains due to inherent flexibility. Blue dashed lines indicate the approximate boundary of the lipid bilayer.
