Entropy-enthalpy compensation at the single protein level: pH sensing in the bacterial channel OmpF.
The pH sensing mechanism of the OmpF channel operates via ligand modification: increasing acidity induces the replacement of cations with protons in critical binding sites decreasing the channel conductance. Aside from the change in enthalpy associated with the binding, there is also a change in the microscopic arrangements of ligands, receptors and the surrounding solvent. We show that the pH-modulation of the single channel conduction involves small free energy changes because large enthalpic and entropic contributions change in opposite ways, demonstrating an approximate enthalpy-entropy compensation for different salts and concentrations.
Department of Physics, Laboratory of Molecular Biophysics, University Jaume I, E-12080 Castellón, Spain. alcaraza@uji.es.
Antonio
A
Alcaraz
María
M
Queralt-Martín
Carmina
C
Verdiá-Báguena
Vicente M
VM
Aguilella
Salvador
S
Mafé
D003198:Computer Simulation; D004553:Electric Conductivity; D019277:Entropy; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D008958:Models, Molecular; D018272:Porins / Q000737:chemistry*; D011189:Potassium Chloride / Q000737:chemistry*
C109237:OmpF protein; D018272:Porins; D011189:Potassium Chloride