Coupling between conformational dynamics and catalytic function at the active site of the lead-dependent ribozyme

Relaxation-dispersion curves. (A) Cyt-6 C2′ (solid); (B) Cyt-6 C4′ (solid). Open symbols in both panels are the helical residue Cyt-28 C2′ for comparison. Fits to the upper curves are to Equations 2 and 3 with R_1ρ fixed to 12.7 sec⁻¹ based on the mean value for helical Cyt-6 C2′. Fits in which was allowed to vary resulted in extremely poor parameter determination. Fit parameters: Cyt-6 C2′, k_ex = (1.0 ± 0.8) × 10⁵ sec⁻¹, Φ_ex = (2.0 ± 1.3) × 10⁶, Δω_min = (3.0 ± 1.0) ppm; Cyt-6 C4′, k_ex = (3.6 ± 0.5) × 10⁴ sec⁻¹, Φ_ex = (9.9 ± 0.7) × 10⁵, Δω_min = (2.1 ± 0.1) ppm.