Fig. 6: Cryo-EM structure of OmpC3-MlaAQ205C-MlaCV171C in nanodiscs.
From: Molecular mechanism of phospholipid transport at the bacterial outer membrane interface
a Front and side orientations of the density map of OmpC3-(MlaA-MlaC)1-3 EMD-35250 (unsharpened; contour level of 0.06, transparency 80%) with the protein surface densities colored green (OmpC; contour level of 0.1) and cyan (MlaA; contour level of 0.1), respectively. b Cartoon illustrations of the OmpC3-MlaA structure PDB: 8I8R well-fitted and refined within protein surface densities in (a) (transparency 80%). c Front and side orientations of the density map of OmpC3-(MlaA-MlaC) EMD-35253 (unsharpened; contour level of 0.06, transparency 80%) with the protein surface densities colored green (OmpC; contour level of 0.1), cyan (MlaA; contour level of 0.1), blue (C-terminal tail helix of MlaA; contour level of 0.06), and pink (MlaC; contour level of 0.06), respectively. d Cartoon illustrations of the OmpC3-MlaA-MlaC structure PDB: 8I8X well-fitted and refined within protein surface densities in (c) (transparency 80%) respectively. Two contact points between MlaA and MlaC are clearly revealed (see (f) inset), one modeled with the engineered MlaAQ205C-MlaCV171C disulfide bond, and the other with the C-terminal linker and tail helix of MlaA. e Cut-away views of the density maps from (a) where the unsharpened nanodisc surface density is now colored gray (transparency 0%) revealed localized membrane thinning in the outer leaflet of the bilayer all around the position of the α-helical ridge of MlaA. f Superimposition of OmpC3-MlaA-MlaC (PDB: 8I8X) and OmpK36-KpMlaA (PDB: 5NUP, red) structures revealed a 7° tilt of MlaA towards the periplasm. Illustrations were generated using UCSF Chimera57.
