Journal
BIOPHYSICAL JOURNAL
Volume 89, Issue 5, Pages 3332-3336Publisher
CELL PRESS
DOI: 10.1529/biophysj.105.067223
Keywords
-
Categories
Funding
- NIGMS NIH HHS [R01 GM059663, GM 059663] Funding Source: Medline
Ask authors/readers for more resources
Normally, isothermal titration calorimetry (ITC) is used to study binding reactions between two different biomolecules. Self-association processes leading to homo-oligomeric complexes have usually not been studied by ITC; instead, methods such as spectroscopy and analytical ultracentrifugation, which only provide affinity and Gibbs-free energy (i.e., K-D and Delta G), are employed. We here demonstrate that complete thermodynamic descriptions (i.e., K-D, Delta G, Delta H, and Delta S) for self-associating systems can be obtained by ITC-dilution experiments upon proper analysis. We use this approach to probe the dissociation ( and thus association) equilibrium for the heptameric co-chaperonin proteins 10 (cpn10) from Aquifex aeolicus (Aacpn10-del25) and human mitochondria (hmcpn10). We find that the midpoints for the heptamer-monomer equilibrium occur at 0.51 +/- 0.03 mu M and 3.5 +/- 0.1 mu M total monomer concentration (25 degrees C), for Aacpn10-del25 and hmcpn10, respectively. For both proteins, association involves endothermic enthalpy and positive entropy changes; thus, the reactions are driven by the entropy increase. This is in accord with the release of ordered water molecules and, for the thermophilic variant, a relaxation of monomer-tertiary structure when the heptamers form.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available