Photoinduced Electron Transfer and Fluorophore Motion as a Probe of the Conformational Dynamics of Membrane Proteins: Application to the Influenza A M2 Proton Channel

• Published in: Langmuir Vol. 27; no. 7; pp. 3815 - 3821
• Main Authors: Rogers, Julie M. G, Polishchuk, Alexei L, Guo, Lin, Wang, Jun, DeGrado, William F, Gai, Feng
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 05.04.2011
• Subjects: Biological Interfaces: Biocolloids, Biomolecular and Biomimetic Materials; Chemistry; Colloidal state and disperse state; Exact sciences and technology; Fluorescence; General and physical chemistry; Hydrogen-Ion Concentration; Liposomes - chemistry; Membrane Proteins - chemistry; Porous materials; Protein Conformation; Spectrometry, Fluorescence - methods; Unilamellar Liposomes - chemistry; Viral Matrix Proteins - chemistry; Binding; Drug; Structure function; Motion; Fluctuations; Dyes; Conformational dynamics; Fluorescence; Electron transfer; Tryptophan; Equilibrium; Porous material; Mechanism; Protein; Fluorophore; Pore; Residue; Proton; pH; Models; Inhibition; Conformational transition
• ISSN: 0743-7463; 1520-5827; 1520-5827
• DOI: 10.1021/la200480d

The structure and function of the influenza A M2 proton channel have been the subject of intensive investigations in recent years because of their critical role in the life cycle of the influenza virus. Using a truncated version of the M2 proton channel (i.e., M2TM) as a model, here we show that fluctuations in the fluorescence intensity of a dye reporter that arise from both fluorescence quenching via the mechanism of photoinduced electron transfer (PET) by an adjacent tryptophan (Trp) residue and local motions of the dye molecule can be used to probe the conformational dynamics of membrane proteins. Specifically, we find that the dynamics of the conformational transition between the N-terminal open and C-terminal open states of the M2TM channel occur on a timescale of about 500 μs and that the binding of either amantadine or rimantadine does not inhibit the pH-induced structural equilibrium of the channel. These results are consistent with the direct occluding mechanism of inhibition which suggests that the antiviral drugs act by sterically occluding the channel pore.