A Genetically Encoded Trimethylsilyl 1D1H-NMR Probe for Conformation Change in Large Membrane Protein Complexes

While one dimensional 1 H nuclear magnetic resonance (1D 1 H-NMR) spectroscopy is one of the most important and convenient method for measuring conformation change in biomacromolecules, characterization of protein dynamics in large membrane protein complexes by 1D 1 H-NMR remains challenging, due to the difficulty of spectra assignment, low signal-to-noise ratio (S/N) and the need for large amount of protein. Here we report the site-specific incorporation of 4-trimethylsilyl phenylalanine (TMSiPhe) into proteins, through genetic code expansion in Escherichia coli cells, and the measurement of multiple conformational states in membrane protein complex by 1D 1 H-NMR. The unique up-field 1 H-NMR chemical shift of TMSiPhe, highly efficient and specific incorporation of TMSiPhe enabled facile assignment of the TMSiPhe 1 H-NMR signal, and characterization of multiple conformational state in a 150 kilodalton (kD) membrane protein complex, using only 5 μM of protein and 20 min spectra accumulation time. This highly efficient and convenient methods should be broadly applicable for the investigation of dynamic conformation change of protein complexes.