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Energetics of cyclic AMP binding to HCN channel C terminus reveal negative cooperativity.

ABSTRACT: Cyclic AMP binds to the HCN channel C terminus and variably stabilizes its open state. Using isothermal titration calorimetry, we show that cAMP binds to one subunit of tetrameric HCN2 and HCN4 C termini with high affinity (?0.12 ?M) and subsequently with low affinity (?1 ?M) to the remaining three subunits. Changes induced by high affinity binding already exist in both a constrained HCN2 tetramer and the unconstrained HCN1 tetramer. Natural "preactivation" of HCN1 may explain both the smaller effect of cAMP on stabilizing its open state and the opening of unliganded HCN1, which occurs as though already disinhibited.

SUBMITTER: Chow SS

PROVIDER: S-EPMC3249114 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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Energetics of cyclic AMP binding to HCN channel C terminus reveal negative cooperativity.

Chow Sarah S SS Van Petegem Filip F Accili Eric A EA

The Journal of biological chemistry 20111114 1

Cyclic AMP binds to the HCN channel C terminus and variably stabilizes its open state. Using isothermal titration calorimetry, we show that cAMP binds to one subunit of tetrameric HCN2 and HCN4 C termini with high affinity (∼0.12 μM) and subsequently with low affinity (∼1 μM) to the remaining three subunits. Changes induced by high affinity binding already exist in both a constrained HCN2 tetramer and the unconstrained HCN1 tetramer. Natural "preactivation" of HCN1 may explain both the smaller e ...[more]

PMID: 22084239

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