FIGURE 1.

SfbI-5 is intrinsically disordered. A, ¹H,¹⁵N HSQC spectrum of ¹⁵N,¹³C-labeled SfbI-5. The peaks in the spectra were assigned to the ¹H^N and ¹⁵N^H resonances of SfbI-5 residues using standard procedures. Each peak is labeled according to its position in the full-length SfbI-5 sequence. The peak annotated I(540) is not native to full-length SfbI but is directly N-terminal to Pro-541 from native SfbI, and the peak annotated R576 is from the side chain of Arg-576. The other smaller unassigned peaks in close proximity to assigned resonances are likely to arise from residues near a proline as a result of the proline being in a cis-conformation. Inset is an enlarged area of the boxed region of the spectrum. B, sequence-corrected SSP score was calculated for SfbI-5 using all available chemical shift information. SSP scores of +1 and −1 represent a stable α-helix and β-strand, respectively. A score of 0 represents random coil.