VDAC1 Conformational Changes Investigated by High Pressure DEER

Abstract

Each day, humans turn over their body-weight equivalent in ATP, most of which is produced in the mitochondria. Thus, ATP and ADP transport in and out of this organelle is critical for a good homeostasis. This transport is mediated by the Voltage-Dependent Anion Channel (VDAC), the most abundant protein of the outer mitochondrial membrane. VDAC is a 19 strand β-barrel, with an open conformation of high anion selective conductance (4 nS) allowing metabolite transport. Various low-conductance states exist (1.6-1.8 nS), which are cation selective and impermeable to metabolites. While several structures of VDAC in the open conformation have been solved, any other conformations, such as the closed states, remain to be identified. Here, we used high hydrostatic pressure, a powerful method to investigate conformational changes in proteins, to stabilize conformations that are otherwise negligibly populated and thus inaccessible to traditional biophysical analysis. Using double electron-electron resonance (DEER) spectroscopy we probed structural changes induced by high pressure on double-labeled mVDAC1, providing a better understanding of the barrel flexibility.