Proton-Detected Solid-State NMR of the Cell-Free Synthesized a-Helical Transmembrane Protein NS4B from Hepatitis C Virus

Proton‐detected 100 kHz magic‐angle‐spinning (MAS) solid‐state NMR is an emerging analysis method for proteins with only hundreds of microgram quantities, and thus allows structural investigation of eukaryotic membrane proteins. This is the case for the cell‐free synthesized hepatitis C virus (HCV) nonstructural membrane protein 4B (NS4B). We demonstrate NS4B sample optimization using fast reconstitution schemes that enable lipid‐environment screening directly by NMR. 2D spectra and relaxation properties guide the choice of the best sample preparation to record 2D 1H‐detected 1H,15N and 3D 1H,13C,15N correlation experiments with linewidths and sensitivity suitable to initiate sequential assignments. Amino‐acid‐selectively labeled NS4B can be readily obtained using cell‐free synthesis, opening the door to combinatorial labeling approaches which should enable structural studies.
Membrane proteins revealed: We show how proton‐detected 100 kHz magic‐angle‐spinning solid‐state NMR can be harnessed for investigation of eukaryotic membrane proteins in lipids. Direct NMR screening of lipid environment on sub‐milligram amounts of protein guide optimal sample preparation. Amino‐acid‐selectively labeled protein from cell‐free synthesis opens the way to structural studies.