Fig. 1: Copper(II) binding to MsbA modulates lipid binding affinity.
From: Structural basis for lipid and copper regulation of the ABC transporter MsbA
a Lipopolysaccharide biosynthesis commences in the cytoplasm to generate lipooligosaccharide (LOS). LOS is composed of conserved lipid A structure (gray), a bisphosphorylated disaccharide of glucosamine, modified with 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) sugar (orange) and core oligosaccharide (purple), of which is dependent on the bacteria. MsbA, powered by the hydrolysis of ATP, flips cytoplasmic LOS from inner to outer leaflet of the inner membrane, an essential step in LPS biogenesis. The flipped LOS is transported to the outer membrane along with additional modifications to become LPS. b Native mass spectrum of optimized MsbA samples in C10E5 yields a well-resolved mass spectrum. c Equilibrium dissociation constants (KD) for individual lipid binding events to partially loaded MsbA. d Deconvolution of the mass spectrum shown in panel b. The different molecular species correspond to dimeric MsbA and different numbers of bound copper ions. e Measured mass of MsbA after loading with copper(II) shows saturation of two binding sites. f KDs for individual lipid binding events to MsbA fully loaded with copper(II). Reported are the mean and standard deviation (n = 3, biological replicates). Source data are provided as a Source Data file.
