Retel, Joren S.Nieuwkoop, Andrew J.Hiller, MatthiasHigman, Victoria A.Barbet-Massin, EmelineStanek, JanAndreas, Loren B.Franks, W. TrentVan Rossum, Barth-JanVinothkumar, Kutti R.Handel, LieselotteDe Palma, Gregorio GiuseppeBardiaux, BenjaminPintacuda, GuidoEmsley, LyndonKuehlbrandt, WernerOschkinat, Hartmut2018-01-152018-01-152018-01-15201710.1038/s41467-017-02228-2https://infoscience.epfl.ch/handle/20.500.14299/144042WOS:000417702300024beta-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 H-1-H-1 and C-13-C-13 distance restraints, 256 torsion angles, but no hydrogen bond restraints are used to calculate the structure. The length of beta-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.text::journal::journal article::research article