Journal article
Comparative thermodynamic analysis of cyclic nucleotide binding to protein kinase A



Publication Details
Authors:
Moll, D.; Schweinsberg, S.; Hammann, C.; Herberg, F.
Publication year:
2007
Journal:
Biological Chemistry
Pages range:
163-172
Volume number:
388
Start page:
163
End page:
172
ISSN:
1431-6730

Abstract
We have investigated the thermodynamic parameters and binding of a regulatory subunit of cAMP-dependent protein kinase (PKA) to its natural low-molecular-weight ligand, cAMP, and analogues thereof. For analysis of this model system, we compared side-by-side isothermal titration calorimetry (ITC) with surface plasmon resonance (SPR). Both ITC and SPR analyses revealed that binding of the protein to cAMP or its analogues was enthalpically driven and characterised by similar free energy values (Delta G = -9.4 to -10.7 kcal mol(-1)) for all interactions. Despite the similar affinities, binding of the cyclic nucleotides used here was characterised by significant differences in the contribution of entropy (-T Delta S) and enthalpy (Delta H) to Delta G. The comparison of ITC and SPR data for one cAMP analogue further revealed deviations caused by the method. These equilibrium parameters could be complemented by thermodynamic data of the transition state (Delta H-not equal, Delta G(not equal), Delta S-not equal) for both association and dissociation measured by SPR. This direct comparison of ITC and SPR highlights method-specific advantages and drawbacks for thermodynamic analyses of protein/ligand interactions.

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