Abstract
The voltage-dependent anion channel (VDAC) is a β-barrel channel of the mitochondrial outer membrane (MOM) that passively transports ions, metabolites, polypeptides, and single-stranded DNA. VDAC responds to a transmembrane potential by "gating,"i.e. transitioning to one of a variety of low-conducting states of unknown structure. The gated state results in nearly complete suppression of multivalent mitochondrial metabolite (such as ATP and ADP) transport, while enhancing calcium transport. Voltage gating is a universal property of β-barrel channels, but VDAC gating is anomalously sensitive to transmembrane potential. Here, we show that a single residue in the pore interior, K12, is responsible for most of VDAC's voltage sensitivity. Using the analysis of over 40 μs of atomistic molecular dynamics (MD) simulations, we explore correlations between motions of charged residues inside the VDAC pore and geometric deformations of the β-barrel. Residue K12 is bistable; its motions between two widely separated positions along the pore axis enhance the fluctuations of the β-barrel and augment the likelihood of gating. Single channel electrophysiology of various K12 mutants reveals a dramatic reduction of the voltage-induced gating transitions. The crystal structure of the K12E mutant at a resolution of 2.6 Å indicates a similar architecture of the K12E mutant to the wild type; however, 60 μs of atomistic MD simulations using the K12E mutant show restricted motion of residue 12, due to enhanced connectivity with neighboring residues, and diminished amplitude of barrel motions. We conclude that β-barrel fluctuations, governed particularly by residue K12, drive VDAC gating transitions.
Original language | English |
---|---|
Pages (from-to) | 14564-14577 |
Number of pages | 14 |
Journal | Journal of the American Chemical Society |
Volume | 144 |
Issue number | 32 |
DOIs | |
State | Published - Aug 17 2022 |
Funding
V.A.N. acknowledges postdoctoral fellowships from Alberta Innovates-Health Solutions (AIHS, 2015–2017), Canadian Institutes of Health Research (CIHR, 2016–2018), and Los Alamos National Lab Director’s Fellowship (2018–2021) for the work on VDAC. M.Q.M., S.M.B., and T.K.R. were supported by the Intramural Research Program of the National Institutes of Health, Eunice Kennedy Shriver National Institute of Child Health and Human Development. M.Q.M. acknowledges a postdoctoral fellowship Juan de la Cierva Incorporación from the Spanish Ministry of Science and Innovation MCIN/AEI/10.13039/501100011033 (IJC2018-035283-I, 2020-2022) and support from Universitat Jaume I (Project UJI-A2020–21). Anton 2 computer time was provided through allocation PSCA16049P to D.P.H. and S.Y.N. by the Pittsburgh Supercomputing Center (PSC) through Grant R01GM116961 from the National Institutes of Health. Beamline 5.0.1 of the Advanced Light Source, a U.S. DOE Office of Science User Facility under Contract No. DE-AC02-05CH11231, is supported in part by the ALS-ENABLE program funded by the National Institutes of Health, National Institute of General Medical Sciences, Grant P30 GM124169-01.