Thermodynamics of steroid binding to the human glucocorticoid receptor

Abstract

The thermodynamics of the interaction of glucocorticoids with their receptor were studied in cytosol from human lymphoblastoid cells. The rate and affinity constants of dexamethasone and cortisol between 0 degree and 25 degrees C were calculated by curve-fitting from time-course and equilibrium kinetics. The data were consistent with a simple reversible bimolecular interaction. Arrhenius and Van't Hoff plots were curvilinear for both steroids. At equilibrium, the solution for the equation delta G = delta H - T X delta S (eqn. 1) was (in kJ X mol-1) -47 = 36 - 83 (dexamethasone) and -42 = -9 - 33 (cortisol) at 0 degree C. Enthalpy and entropy changes decreased quasi-linearly with temperature such that, at 25 degrees C, the respective values were -50 = -75 + 25 and -43 = -48 + 5. Thus, for both steroids, the interaction was entropy-driven at low temperature and became entirely enthalpy-driven at 20 degrees C. Thermodynamic values for the transition state were calculated from the rate constants. For the forward reaction, eqn. (1) gave 45 = 84 - 39 (dexamethasone) and 46 = 60 - 14 (cortisol) at 0 degree C, and 44 = 24 + 20 (dexamethasone) and 46 = 28 + 18 (cortisol) at 25 degrees C. These data fit quite well with a two-step model [Ross & Subramanian (1981) Biochemistry 20, 3096-3102] proposed for ligand-protein interactions, which involves a partial immobilization of the reacting species governed by hydrophobic forces, followed by stabilization of the complex by short-range interactions. On the basis of this model, an analysis of the transition-state thermodynamics led to the conclusion that no more than half of the steroid molecular area is engaged in the binding process.

Temperature‐dependence of the kinetics of the binding of [3H]‐(+)‐N‐methyl‐4‐methyldiphenhydramine to the histamine H1‐receptor: comparison with the kinetics of [3H]‐mepyramine

“…The second simplifying feature of the kinetics of both [3H]-QMDP and [3H]-mepyramine is that Arrhenius plots for k1 and k-1 are linear over the temperature range studied. There is no indication of any discontinuity in the region of the membranetransition temperature, such is observed with a2 antagonists (Lohse et al, 1986) or of a more complex situation, such as that indiated by curvilinear Arrhenius plots for glucocorticoid binding to the cytosolic receptor (Eliard & Rousseau, 1984). The linearity of the Arrhenius plots for k-1 for both -mepyramine is particularly clear (Figures 3 and 9).…”

Purification and functional characterization of the ligand-binding domain from the retinoic acid receptor alpha: Evidence that sulfhydryl groups are involved in ligand-receptor interactions

“…At low temperatures, the retinoid-receptor interaction is mainly entropy driven, as already described with the glucocorticoid receptor (Wolff et ai. 1978;Eliard & Rousseau, 1984). Binding data reveal that only 1.5 nmol of functional GSThRARa LBD could be produced per liter of bacterial culture.…”

Binding thermodynamics at the human cannabinoid CB1 and CB2 receptors

“…A c c e p t e d M a n u s c r i p t 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 in solution but appears to be typical as far as membrane receptor binding is concerned [27]. 2) Cp° is not equal to zero [9,28]. In this case the plot G° versus T is often parabolic and other mathematical methods for calculating the thermodynamic parameters of the equilibrium are available.…”

“…in solution but appears to be typical as far as membrane receptor binding is concerned [27]. 2) Cp° is not equal to zero [9,28]. In this case the plot G° versus T is often parabolic and other mathematical methods for calculating the thermodynamic parameters of the equilibrium are available.…”