Demystifying thermal channels: Driving a channel both forwards and backwards with a single gear?

摘要

Thermal TRPs-a group of ion channels from the TRP superfamily-spend their lives on monitoring ambient temperature. As such, their opening has become exquisitely sensitive to temperature changes. How can a channel acquire such sharp temperature dependence? As a simplified conceptual framework for discussion, we can consider the Boltzmann equation, which for a two-state closed-open system predicts P_0 = 1/[1+exp(-DELTAH/RT + DELTAS/R)]. In the other words, the opening of a channel relates to temperature via the enthalpy change (AH) between closed and open states. Specifically, the enthalpy determines the slope of their gating curve with respect to temperature, whereas the entropy (AS) sets the operation point. Given this view, how large an enthalpy change can an ion channel have? The textbooks say that enzymatic reactions generally have a Q_(10) ~ 2-3.