VDAC PROPERTIES ARE INFLUENCED BY THE SOURCE OF ITS PURIFICATION

Objectives: The Voltage Dependent Anion-Selective Channel (VDAC), the most abundant protein of the outer mitochondrial membrane (OMM), forms the major conduit for metabolite transport across this membrane. It has also been shown to be involved in cell death signalling through interaction with other proteins like Hexokinase and by mediating release of apoptogenic proteins like cyt c from mitochondria. As in case of other channel proteins, functional characterization of purified reconstituted protein by using electrophysiological techniques can be used in development of VDAC targeted drugs. Here we report electrophysiological properties of VDACs (one of the target for cancerous cells) purified from different sources. Methods: Human VDAC1 and rice VDAC4 were heterologously expressed and purified from E. coli BL21 (DE3)-pLysS, while rat and yeast VDACs were purified from mitochondria. Electrophysiological studies of all VDACs were done by using BLM and the data was analysed by using pCLAMP 10 (Axon Instruments). Results: VDACs purified from both the sources showed conserved voltage dependence and channel conductance, however they showed significant difference in dynamics. VDAC purified from mitochondria had relatively short occupancy of each electrophysiological state compared to protein purified from inclusion bodies. Conclusion: Our results suggest that the source of purified protein could be critical for some aspects of channel function