Protonation equilibria and pore-opening structure of the dual-histidine influenza B virus M2 transmembrane proton channel from solid-state NMR
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BM2 H27F5 v6.pdf
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Author(s)
Wang, Jun
Williams, Jonathan Kyle
Shcherbakov, Alexander Aleksandrovich
Hong, Mei
Date Issued
September 2017
Journal
Journal of Biological Chemistry
Publisher
American Society for Biochemistry and Molecular Biology (ASBMB)
Citation
Williams, Jonathan K. et al. “Protonation Equilibria and Pore-Opening Structure of the Dual-Histidine Influenza B Virus M2 Transmembrane Proton Channel from Solid-State NMR.” Journal of Biological Chemistry 292, 43 (September 2017): 17876–17884 © 2017 by The American Society for Biochemistry and Molecular Biology, Inc
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Author's final manuscript
Abstract
The influenza A and B viruses are the primary cause of seasonal flu epidemics. Common to both viruses is the M2 protein, a homotetrameric transmembrane proton channel that acidifies the virion after endocytosis. Although influenza A M2 (AM2) and B M2 (BM2) are functional analogs, they have little sequence homology, except for a conserved HXXXW motif, which is responsible for proton selectivity and channel gating. Importantly, BM2 contains a second titratable histidine, His-27, in the tetrameric transmembrane domain that forms a reverse WXXXH motif with the gating tryptophan. To understand how His-27 affects the proton conduction property of BM2, we have used solid-state NMR to characterize the pH-dependent structure and dynamics of His-27. In cholesterol-containing lipid membranes mimicking the virus envelope, ¹⁵N NMR spectra show that the His-27 tetrad protonates with higher pKa values than His-19, indicating that the solvent-accessible His-27 facilitates proton conduction of the channel by increasing the proton dissociation rates of His-19. AM2 is inhibited by the amantadine class of antiviral drugs, whereas BM2 has no known inhibitors. We measured the N-terminal interhelical separation of the BM2 channel using fluorinated Phe-5. The interhelical ¹⁹F-¹⁹F distances show a bimodal distribution of a short distance of 7 Å and a long distance of 15–20 Å, indicating that the phenylene rings do not block small-molecule entry into the channel pore. These results give insights into the lack of amantadine inhibition of BM2 and reveal structural diversities in this family of viral proton channels. Keywords: influenza virus; ion channel; membrane protein; solid state NMR; structural biology
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1074/jbc.M117.813998
