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Publication Abstract from PubMed

beta-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 (1)H-(1)H and (13)C-(13)C 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.

Structure of outer membrane protein G in lipid bilayers.,Retel JS, Nieuwkoop AJ, Hiller M, Higman VA, Barbet-Massin E, Stanek J, Andreas LB, Franks WT, van Rossum BJ, Vinothkumar KR, Handel L, de Palma GG, Bardiaux B, Pintacuda G, Emsley L, Kuhlbrandt W, Oschkinat H Nat Commun. 2017 Dec 12;8(1):2073. doi: 10.1038/s41467-017-02228-2. PMID:29233991^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.