Backbone Assignment of a 28.5 kDa Class A Extended Spectrum β-Lactamase by High-Field, Carbon-Detected Solid-State NMR.

C and N backbone chemical shift assignments are reported for the 28.5 kDa protein Toho-1 β-lactamase, a Class A extended spectrum β-lactamase. A very high level of assignment completeness (97% of the backbone) is enabled by the combined sensitivity and resolution gains of ultrahigh-field NMR spectroscopy (1.1 GHz), improved probe technology, and optimized pulse sequences. The assigned chemical shifts agree well with our previous solution-state NMR assignments, indicating that the secondary structure is conserved in the solid state. These assignments provide a foundation for future investigations of sidechain chemical shifts and catalytic mechanism.