Temperature dependence of acetylcholine receptor channels activated by different agonists

Shaweta Gupta, Anthony Auerbach

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Abstract

The temperature dependence of agonist binding and channel gating were measured for wild-type adult neuromuscular acetylcholine receptors activated by acetylcholine, carbamylcholine, or choline. With acetylcholine, temperature changed the gating rate constants (Q10 ≈ 3.2) but had almost no effect on the equilibrium constant. The enthalpy change associated with gating was agonist-dependent, but for all three ligands it was approximately equal to the corresponding free-energy change. The equilibrium dissociation constant of the resting conformation (Kd), the slope of the rate-equilibrium free-energy relationship (Φ), and the acetylcholine association and dissociation rate constants were approximately temperature-independent. In the mutant αG153S, the choline association and dissociation rate constants were temperature-dependent (Q10 ≈ 7.4) but Kd was not. By combining two independent mutations, we were able to compensate for the catalytic effect of temperature on the decay time constant of a synaptic current. At mouse body temperature, the channel-opening and-closing rate constants are ∼400 and 16 ms∼-1. We hypothesize that the agonist dependence of the gating enthalpy change is associated with differences in ligand binding, specifically to the open-channel conformation of the protein.

Original languageEnglish (US)
Pages (from-to)895-903
Number of pages9
JournalBiophysical journal
Volume100
Issue number4
DOIs
Publication statusPublished - Feb 16 2011

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All Science Journal Classification (ASJC) codes

  • Biophysics

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