Temperature-dependent conformational changes in a voltage-gated potassium channel

Temperature was used as a biophysical tool to investigate the energy changes associated with conformational change during the gating of a non-inactivating voltage-gated K+ channel present in the membrane of alpha T3-1 cells, a gonadotroph cell line. The time course of the current activation was described by a single exponential function at three temperatures: 15, 25 and 35 degrees C. The Q10 values were between 1.5 to 1.9 and in agreement with the activation energy determined from Arrhenius plots of the forward and backward rate constants associated with channel opening. The Gibb's free energy change associated with channel opening and closing at various membrane potentials estimated by two approaches yield similar values. The changes in Gibb's free energy (delta G degree) with depolarization potential is a quadratic and more prominent at 15 than at 25 or 35 degrees C. The results suggest that increase in temperature favours movement of voltage sensing segments, and reduces the restraint on them brought about by other parts of the channel molecule.