Abstract
The voltage-dependent anion channel (VDAC) is the major pathway for metabolites and ions transport through the mitochondrial outer membrane. It can regulate the flow of solutes by switching to a low conductance state correlated with a selectivity reversal, or by a selectivity inversion of its open state. The later one was observed in non-plant VDACs and is poorly characterized. We aim at investigating the selectivity inversion of the open state using plant VDAC purified from Phaseolus coccineus (PcVDAC) to evaluate its physiological role. Our main findings are: (1) The VDAC selectivity inversion of the open state occurs in PcVDAC, (2) Ion concentration and stigmasterol affect the occurrence of the open state selectivity inversion and stigmasterol appears to interact directly with PcVDAC. Interestingly, electrophysiological data concerning the selectivity inversion of the PcVDAC open state suggests that the phenomenon probably does not have a significant physiological effect in vivo.
Highlights
The exchange of inorganic ions and metabolites between the mitochondria and the cytosol is essential for numerous mitochondrial functions
Ten-fold (1/0.1 M) KCl gradient was formed by decreasing the KCl concentration in the Cis compartment, and the current flowing through the PcVDAC in response to a linear voltage ramp was recorded
The regulation of the voltage-dependent anion channel (VDAC) selectivity is an essential functional process for the control of metabolite flow through mitochondrial outer membrane (MOM), notably for ATP
Summary
The exchange of inorganic ions and metabolites between the mitochondria and the cytosol is essential for numerous mitochondrial functions. The voltage-dependent anion channel (VDAC) is the major transport pathway in the mitochondrial outer membrane (MOM) for compounds as diverse as inorganic ions (e.g., K+, Na+ and Cl−), metabolites (e.g., ATP and AMP) and large macromolecules such as tRNA [6]. The modification of the membrane lipid composition is a hallmark of plant stress responses and its effect on mitochondria function has long been recognized [11,12,13]. Only stigmasterol alters the voltage-dependence of the PcVDAC [20]. This indicates that lipid-protein interactions are important for the proper functioning of PcVDAC
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