VDAC Gating Thermodynamics, but Not Gating Kinetics, Are Virtually Temperature Independent
Maria Queralt-Martin, David Hoogerheide, Sergei Y. Noskov, Alexander M. Berezhkovskii, Tatiana Rostovtseva, Sergey Bezrukov
The voltage-dependent anion channel, VDAC, is the most abundant protein in the mitochondrial outer membrane and an archetypical β-barrel channel. Here, we study the effects of temperature on VDAC channels reconstituted in planar lipid membranes at the single- and multi-channel levels within the 20°C – 40°C range. The temperature dependence of conductance, measured on a single channel in 1 M KCl, shows an increase characterized by a 10°C temperature coefficient Q10=1.22 plus or minus}0.02, which exceeds that of the bathing electrolyte solution conductivity, Q10=1.17plus or minus}0.01. The rates of voltage-induced channel transition between the open and closed states, measured on multichannel membranes, also show statistically significant increases with temperature that are consistent with activation energy barriers of about 10 plus or minus} 3 kcal/mol. At the same time, the gating thermodynamics, as characterized by the gating charge and voltage of equipartitioning, does not display any measurable temperature dependence. The two parameters stay within 3.2 plus or minus} 0.2 elementary charges and 30 plus or minus} 2 mV, correspondingly. Thus, while the channel kinetics— specifically, its conductance and the rates of transitions between open and closed states— demonstrate a clear increase with temperature, the conformational voltage-dependent equilibria are virtually insensitive to temperature. These results, which may be a general feature of β-barrel channel gating, suggest either an entropy-driven gating mechanism or a role for enthalpy-entropy compensation.
Voltage Dependent Anion Channel, voltage gating, thermodynamics, planar lipid membrane, channel reconstitution
, Hoogerheide, D.
, Noskov, S.
, Berezhkovskii, A.
, Rostovtseva, T.
and Bezrukov, S.
VDAC Gating Thermodynamics, but Not Gating Kinetics, Are Virtually Temperature Independent, Biophysical Journal
(Accessed December 10, 2023)