Solid-state NMR of a protein in a precipitated complex with a full-length antibody

NMR is a prime technique for characterizing atomic resolution structures and dynamics of biomolecular complexes but, for such systems, faces challenges of sensitivity and spectral resolution. We demonstrate that application of (1)H-detected experiments at <50 kHz magic angle spinning frequencies enables the recording, in a matter of minutes to hours, of solid-state NMR spectra suitable for quantitative analysis of protein complexes present in quantities as small as a few nanomoles (tens of micrograms for the observed component). This approach enables direct structure determination and quantitative dynamics measurements in domains of hundreds-of-kDa protein complexes. Protein-protein interaction interfaces can be mapped out by comparing the chemical shifts of proteins within solid-state complexes with those of the same constituent proteins free in solution. We employ this methodology to characterize a <300 kDa complex of GB1 with full-length human immunoglobulin, where we find that sample preparation by simple precipitation yields spectra of exceptional quality, a feature that is likely to be shared with some other precipitating complexes. Finally, we investigate extensions of our methodology to spinning frequencies of up to 100 kHz.