Conformational analysis of the full-length M2 protein of the influenza a virus using solid-state NMR.
Related Articles Conformational analysis of the full-length M2 protein of the influenza a virus using solid-state NMR.
Protein Sci. 2013 Sep 10;
Authors: Liao SY, Fritzsching KJ, Hong M
Abstract
The influenza A M2 protein forms a proton channel for virus infection and mediates virus assembly and budding. While extensive structural information is known about the transmembrane (TM) helix and an adjacent amphipathic helix (AH), the conformation of the N-terminal ectodomain and the C-terminal cytoplasmic tail remains largely unknown. Using 2D magic-angle-spinning (MAS) solid-state NMR, we have investigated the secondary structure and dynamics of full-length M2 (M2FL) and found them to depend on the membrane composition. In 2D (13) C DARR correlation spectra, DMPC-bound M2FL exhibits several peaks at ?-sheet chemical shifts, which result from water-exposed extra-membrane residues. In contrast, M2FL bound to cholesterol-containing membranes gives predominantly ?-helical chemical shifts. 2D J-INADEQUATE spectra and variable-temperature (13) C spectra indicate that DMPC-bound M2FL is highly dynamic while the cholesterol-containing membranes significantly immobilize the protein at physiological temperature. Chemical-shift prediction for various secondary-structure models suggests that the ?-strand is located at the N-terminus of the DMPC-bound protein, while the cytoplasmic domain is unstructured. This prediction is confirmed by the 2D DARR spectrum of the ectodomain-truncated M2(21-97), which no longer exhibits ?-sheet chemical shifts in the DMPC-bound state. We propose that the M2 conformational change results from the influence of cholesterol, and the increased helicity of M2FL in cholesterol-rich membranes may be relevant for M2 interaction with the matrix protein M1 during virus assembly and budding. The successful determination of the ?-strand location suggests that chemical-shift prediction is a promising approach for obtaining structural information of disordered proteins before resonance assignment.
PMID: 24023039 [PubMed - as supplied by publisher]
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