For heterogeneous and insoluble systems that are difficult for X-ray diffraction and solution NMR to characterize, solid-state NMR presents a powerful technique for native-state studies. Membrane protein, associated with the membrane environment, represents a system with special advantages for solid-state NMR. In this thesis, we have applied various solid-state NMR techniques to study the structure and dynamics of the transmembrane domain (TM) of M2 protein of influenza A Udorn strain in lipid bilayers.

The M2 protein of influenza A virus (AM2) forms a tetrameric proton channel on the virus membrane and plays an important role in the influenza virus life cycle. The elucidation of its functional mechanism may have a great impact on the public health. By applying ¹³C{¹⁵N} REDOR and DIPSHIFT experiments, we have determined the conformations and dynamics of a key His37 residue of the AM2 TM channel in both closed and conducting states and a proton gating and conduction mechanism has been proposed. Furthermore, the conformational plasticity of the AM2 TM backbone in lipid bilayers has been studied under various external conditions with 2D homonuclear (DARR) and heteronuclear (HETCOR) correlation experiments. Three sets of chemicals-shift-derived backbone conformations were identified that may be important for the channel function. Finally, to investigate the His37-activation process of the AM2 channel, we extracted four pKa values of the His37 tetrad by quantifying the side chain ¹⁵N intensity changes with pH in the ¹H-¹⁵N CP experiments and gained information on the pH-dependent distribution and the relative conductivity of each charged state by correlating with electrophysiological results.