Thermodynamics of activation gating in olfactory-type cyclic nucleotide-gated (CNGA2) channels.

ABSTRACT: Olfactory-type cyclic nucleotide-gated (CNG) ion channels open by the binding of cyclic nucleotides to a binding domain in the C-terminus. Employing the Eyring rate theory, we performed a thermodynamic analysis of the activation gating in homotetrameric CNGA2 channels. Lowering the temperature shifted the concentration-response relationship to lower concentrations, resulting in a decrease of both the enthalpy DeltaH and entropy DeltaS upon channel opening, suggesting that the order of an open CNGA2 channel plus its environment is higher than that of the closed channel. Activation time courses induced by cGMP concentration jumps were used to study thermodynamics of the transition state. The activation enthalpies DeltaH++ were positive at all cGMP concentrations. In contrast, the activation

SUBMITTER: Nache V 

PROVIDER: S-EPMC2527250 | biostudies-literature | 2008 Sep

REPOSITORIES: biostudies-literature