Structural-derived energetic parameters calculated based on the crystal structures of N-terminal truncated forms of RIα.

Experimental values for cAMP-free (apo)-RIα(92–381); Tm = 62.5±0.1°C, ΔH = 111.6±2.9 kcal/mol and ΔHVH = 96.3±2.1 kcal/mol.Experimental values for cAMP-bound RIα(92–381); Tm = 71.0±0.1°C, ΔH = 120.4±1.2 kcal/mol and ΔHVH = 139.9±1.4 kcal/mol (with 800 µM cAMP; 4 µM RIα(92–381)).*The cGMP present in site A was not included the calculations.**The C structure was not included in the calculations.Theoretical values for the unfolding heat capacity (ΔCp_calc) and enthalpy changes at 60°C (ΔHcalc_60) and at the Tm (ΔHcalc_at Tm) were calculated from the changes in apolar and polar accessible surface area (ΔASAap and ΔASApol) upon unfolding using structure-energetics correlations (see [22] for equations).