TY - JOUR
T1 - Structural energetics of peptide recognition
T2 - Angiotensin II/antibody binding
AU - Murphy, Kenneth P.
AU - Xie, Dong
AU - Garcia, K. Christopher
AU - Amzel, L. Mario
AU - Freire, Ernesto
PY - 1993/2
Y1 - 1993/2
N2 - The ability to predict the strength of the association of peptide hormones or other ligands with their protein receptors is of fundamental importance in the fields of protein engineering and rational drug design. To form a tight complex between a flexible peptide hormone and its receptor, the large loss of configurational entropy must be overcome. Recently, the crystallographic structure of the complex between angiotensin II and the Fab fragment of a high affinity monoclonal antibody has been determined (Garcia, K. C., Ronco, P. M., Verroust, P. J., Brünger, A. T., Amzel, L. M. Three‐dimensional structure of an angiotensin II–Fab complex at 3 Å: Hormone recognition by an anti‐idiotypic antibody. Science 257:502–507, 1992). In this paper we present a study of the thermodynamics of the association by high sensitivity isothermal titration calorimetry. The results of the experiments indicate that at 30°C the binding is characterized by (1) a ΔH of −8.9 ± 0.7 kcal mol−1, (2) a ΔCp of −240 ± 20 cal K−1 mol−1, and (3) the release of 1.1 ± 0.1 protons per binding site in the pH range 6.0–7.3. Using these values and the previously determined binding constant in phosphate buffer, ΔG at 30°C is estimated as −11 kcal mol−1 and ΔS as 6.9 cal K−1 mol−1. The calorimetric data indicate that binding is favored both enthalpically and entropically. These results have been complemented by structural thermodynamic calculations. The calculated and experimentally determined thermodynamic quantities are in good agreement. Entropically, the loss of configurational entropy is more than compensated by the entropy gain from solvent release associated with the hydrophobic effect. Enthalpically, binding is favored by polar interactions (hydrogen bonding). Consequently, the problem of binding flexible hormones is solved in much the same way as the folding of an unstructured polypeptide chain into a globular protein. © 1993 Wiley‐Liss, Inc.
AB - The ability to predict the strength of the association of peptide hormones or other ligands with their protein receptors is of fundamental importance in the fields of protein engineering and rational drug design. To form a tight complex between a flexible peptide hormone and its receptor, the large loss of configurational entropy must be overcome. Recently, the crystallographic structure of the complex between angiotensin II and the Fab fragment of a high affinity monoclonal antibody has been determined (Garcia, K. C., Ronco, P. M., Verroust, P. J., Brünger, A. T., Amzel, L. M. Three‐dimensional structure of an angiotensin II–Fab complex at 3 Å: Hormone recognition by an anti‐idiotypic antibody. Science 257:502–507, 1992). In this paper we present a study of the thermodynamics of the association by high sensitivity isothermal titration calorimetry. The results of the experiments indicate that at 30°C the binding is characterized by (1) a ΔH of −8.9 ± 0.7 kcal mol−1, (2) a ΔCp of −240 ± 20 cal K−1 mol−1, and (3) the release of 1.1 ± 0.1 protons per binding site in the pH range 6.0–7.3. Using these values and the previously determined binding constant in phosphate buffer, ΔG at 30°C is estimated as −11 kcal mol−1 and ΔS as 6.9 cal K−1 mol−1. The calorimetric data indicate that binding is favored both enthalpically and entropically. These results have been complemented by structural thermodynamic calculations. The calculated and experimentally determined thermodynamic quantities are in good agreement. Entropically, the loss of configurational entropy is more than compensated by the entropy gain from solvent release associated with the hydrophobic effect. Enthalpically, binding is favored by polar interactions (hydrogen bonding). Consequently, the problem of binding flexible hormones is solved in much the same way as the folding of an unstructured polypeptide chain into a globular protein. © 1993 Wiley‐Liss, Inc.
KW - calorimetry
KW - drug design
KW - protein–hormone interaction
KW - thermodynamics
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U2 - 10.1002/prot.340150203
DO - 10.1002/prot.340150203
M3 - Article
C2 - 8441749
AN - SCOPUS:0027537127
SN - 0887-3585
VL - 15
SP - 113
EP - 120
JO - Proteins: Structure, Function, and Bioinformatics
JF - Proteins: Structure, Function, and Bioinformatics
IS - 2
ER -