Assessment of a Large Enzyme–Drug Complex by Proton‐Detected Solid‐State NMR Spectroscopy without Deuteration

Solid‐state NMR spectroscopy has recently enabled structural biology with small amounts of non‐deuterated proteins, largely alleviating the classical sample production demands. Still, despite the benefits for sample preparation, successful and comprehensive characterization of complex spin systems in the few cases of higher‐molecular‐weight proteins has thus far relied on traditional 13C‐detected methodology or sample deuteration. Herein we show for a 29 kDa carbonic anhydrase:acetazolamide complex that different aspects of solid‐state NMR assessment of a complex spin system can be successfully accessed using a non‐deuterated, 500 μg sample in combination with adequate spectroscopic tools. The shown access to protein structure, protein dynamics, as well as biochemical parameters in amino acid sidechains, such as histidine protonation states, will be transferable to proteins that are not expressible in E. coli. The faster, the better? Fast magic angle spinning (MAS) makes solid‐state NMR characterization of complex proteins possible even in the absence of deuteration. It is shown for a 29 kDa complex of hCAII:acetazolamide that structure, dynamics, as well as side‐chain proton characteristics become accessible despite a large facilitation of sample production.