Structure of outer membrane protein G in lipid bilayers.

All relevant data necessary for producing the samples, assigning the protein signals, and calculating the structures are available from the corresponding author upon reasonable request. The NMR data and protein structure are deposited in the BioMagResBank (BMRB) with ID 34088 and the Protein Data Bank (PDB) with ID 5MWV, respectively. The script is deposited in GitHub and can be downloaded under: https://github.com/jorenretel/ompg_restraint_generation. ; β-barrel proteins mediate nutrient uptake in bacteria and serve vital functions in cell signaling and adhesion. For the 14-strand outer membrane protein G of Escherichia coli, opening and closing is pH-dependent. Different roles of the extracellular loops in this process were proposed, and X-ray and solution NMR studies were divergent. Here, we report the structure of outer membrane protein G investigated in bilayers of E. coli lipid extracts by magic-angle-spinning NMR. In total, 1847 inter-residue 1H-1H and 13C-13C distance restraints, 256 torsion angles, but no hydrogen bond restraints are used to calculate the structure. The length of β-strands is found to vary beyond the membrane boundary, with strands 6-8 being the longest and the extracellular loops 3 and 4 well ordered. The site of barrel closure at strands 1 and 14 is more disordered than most remaining strands, with the flexibility decreasing toward loops 3 and 4. Loop 4 presents a well-defined helix. ; This work was supported from a Joint Research Activity in the 7th Framework program of the EC (BioNMR No. 261863), the EU-project iNext (infrastructure for NMR, EM, and X-rays for Translational Research, GA 653706), and the Deutsche Forschungs-gemeinschaft (SFB 740 and OS106/9). A.J.N. was supported by fellowships from the Fulbright Program and the Alexander von Humboldt Foundation. ; Peer-reviewed ; Publisher Version