Figure 5.

Motions at μs - ms timescale in inteins. ¹⁵N R₂/R₁values are plotted versus amide proton-nitrogen residual dipolar coupling, D_HN, for ΔΔIhh-V67CM (a) and Δ ΔIhh-L67CM (b). L428 and T430 clearly have contributions from chemical exchange due to motions at μs to ms timescale. (c) Temperature dependence of ¹⁵N-¹H HSQC. The H429 peak becomes stronger at higher temperature, demonstrating the effect of chemical exchange and the transition from intermediate to fast timescale for chemical exchange with increasing temperature. (d) NH₂ groups in ¹⁵N-¹H HSQC of inteins. The cross peaks for the NH₂ group of N440 are much weaker than other peaks and those of Q51, suggesting the effect of chemical exchange. (e) CPMG dispersion curve for E426 obtained at 293 K and at both 800 MHz (solid circles ‘●’) and 600 MHz (open circles ‘○ ’) and their associated fitting curves. (e) CPMG curve for A65 obtained at 293 K and at both 800 MHz (solid circles ‘● ’) and 600 MHz (open circles ‘○ ’) shows no dispersions. (g) Locations of nitrogen nuclei experiencing μs - ms timescale motion in the intein structure. Amide nitrogen nuclei with R_ex (blue spheres) are clustered near the turn formed by the hydrogen bond (red dashed line) between E426 CO and H429 NH. Residues with R_ex, including amides of conserved H429 and N440 are located at the C-terminal splicing junction. It is noteworthy that the N-terminal splicing junction (C1) is nearby as well.