Abstract

In mammals, temperature-sensitive TRP channels make membrane conductance of cells extremely temperature dependent, allowing the detection of temperature ranging from noxious cold to nox-ious heat. We progressively deleted the distal carboxyl terminus domain (CTD) of the cold-activated melastatin receptor channel, TRPM8. We found that the enthalpy change associated with chan-nel gating is proportional to the length of the CTD. Deletion of the last 36 amino acids of the CTD transforms TRPM8 into a reduced temperature-sensitivity channel (Q(10) similar to 4). Exposing the intracellu-lar domain to a denaturing agent increases the energy required to open the channel indicating that cold drives channel gating by stabilizing the folded state of the CTD. Experiments in the pres-ence of an osmoticant agent suggest that channel gating involves a change in solute-inaccessible volume in the CTD of similar to 1,900 angstrom(3). This volume matches the void space inside the coiled coil according to the cryogenic electron microscopy structure of TRPM8. The re-sults indicate that a folding-unfolding reaction of a specialized temperature-sensitive structure is coupled to TRPM8 gating.