Pico-to-microsecond and millisecond structural dynamics of TIL′E′. (A) Backbone TIL′E′ {¹H}¹⁵N heteronuclear NOEs that report on motions on the subnanosecond timescale. Low values indicate flexible, unstructured regions, whereas stabilizing structural elements give rise to higher hetNOEs. Secondary-structure elements of TIL′E′ are depicted below the plot. (B) Simultaneous stereo representation of the structure and pico-to-microsecond dynamics (gray) overlaid with the lowest-energy structure from the single-structure calculations (TIL′, blue; E′, red). The stereo mode is wall-eye. (C) Nitrogen backbone millisecond chemical exchange contributions, ⁠, obtained at 700 MHz. Significant exchange contributions, R_ex, indicate dynamics on a microsecond to millisecond timescale (conformational exchange). Backbone millisecond dynamics are almost entirely confined to the TIL′ domain, with the E′ domain comparatively rigid on this timescale. (D) Combined dynamics of TIL′E′; orange balls represent residues with {¹H}¹⁵N NOE <0.6, whereas the backbone ribbon is colored red (blue) for residues whose R_ex is greater (less) than 1.5 s⁻¹. The backbone for residues where no R_ex is available is colored gray. (E) Two representative dispersion profiles of residues with millisecond structural dynamics, Cys776 and Ser806. Points (vertical bars) represent measured R_ex values (uncertainties), and the full-drawn line is a least-squares fit of a 2-site conformational exchange model to the data shown (red. 700 MHz; black, 500 MHz).