title: Markov chain Monte Carlo based analysis of post-translationally modified VDAC gating kinetics.
abstract: The voltage-dependent anion channel (VDAC) is the main conduit for permeation of solutes (including nucleotides and metabolites) of up to 5 kDa across the mitochondrial outer membrane (MOM). Recent studies suggest that VDAC activity is regulated via post-translational modifications (PTMs). Yet the nature and effect of these modifications is not understood. Herein, single channel currents of wild-type, nitrosated, and phosphorylated VDAC are analyzed using a generalized continuous-time Markov chain Monte Carlo (MCMC) method. This developed method describes three distinct conducting states (open, half-open, and closed) of VDAC activity. Lipid bilayer experiments are also performed to record single VDAC activity under un-phosphorylated and phosphorylated conditions, and are analyzed using the developed stochastic search method. Experimental data show significant alteration in VDAC gating kinetics and conductance as a result of PTMs. The effect of PTMs on VDAC kinetics is captured in the parameters associated with the identified Markov model. Stationary distributions of the Markov model suggest that nitrosation of VDAC not only decreased its conductance but also significantly locked VDAC in a closed state. On the other hand, stationary distributions of the model associated with un-phosphorylated and phosphorylated VDAC suggest a reversal in channel conformation from relatively closed state to an open state. Model analyses of the nitrosated data suggest that faster reaction of nitric oxide with Cys-127 thiol group might be responsible for the biphasic effect of nitric oxide on basal VDAC conductance.
authors: Department of Molecular and Integrative Physiology, University of Michigan Ann Arbor, MI, USA.
authors: Shivendra G
authors: SG
authors: Tewari
authors: HD Biosciences Corporation Shanghai, China.
authors: Yifan
authors: Y
authors: Zhou
authors: Department of Anesthesiology, Medical College of Wisconsin Milwaukee, WI, USA.
authors: Bradley J
authors: BJ
authors: Otto
authors: Department of Physiology, Medical College of Wisconsin Milwaukee, WI, USA ; Biotechnology and Bioengineering Center, Medical College of Wisconsin Milwaukee, WI, USA.
authors: Ranjan K
authors: RK
authors: Dash
authors: Department of Anesthesiology, Medical College of Wisconsin Milwaukee, WI, USA ; Department of Pharmacology and Toxicology, Medical College of Wisconsin Milwaukee, WI, USA.
authors: Wai-Meng
authors: WM
authors: Kwok
authors: Department of Molecular and Integrative Physiology, University of Michigan Ann Arbor, MI, USA.
authors: Daniel A
authors: DA
authors: Beard
keywords: MCMC; VDAC; electrophysiology; lipid bilayer; mitochondria; nitrosation; phosphorylation
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