title: Affixing N-terminal α-helix to the wall of the voltage-dependent anion channel does not prevent its voltage gating.
abstract: The voltage-dependent anion channel (VDAC) governs the free exchange of ions and metabolites between the mitochondria and the rest of the cell. The three-dimensional structure of VDAC1 reveals a channel formed by 19 β-strands and an N-terminal α-helix located near the midpoint of the pore. The position of this α-helix causes a narrowing of the cavity, but ample space for metabolite passage remains. The participation of the N-terminus of VDAC1 in the voltage-gating process has been well established, but the molecular mechanism continues to be debated; however, the majority of models entail large conformational changes of this N-terminal segment. Here we report that the pore-lining N-terminal α-helix does not undergo independent structural rearrangements during channel gating. We engineered a double Cys mutant in murine VDAC1 that cross-links the α-helix to the wall of the β-barrel pore and reconstituted the modified protein into planar lipid bilayers. The modified murine VDAC1 exhibited typical voltage gating. These results suggest that the N-terminal α-helix is located inside the pore of VDAC in the open state and remains associated with β-strand 11 of the pore wall during voltage gating.
authors.affiliation: Program in Physical Biology, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Oscar
authors.initials: O
authors.lastname: Teijido
authors.forename: Rachna
authors.initials: R
authors.lastname: Ujwal
authors.forename: Carl-Olof
authors.initials: CO
authors.lastname: Hillerdal
authors.forename: Lisen
authors.initials: L
authors.lastname: Kullman
authors.forename: Tatiana K
authors.initials: TK
authors.lastname: Rostovtseva
authors.forename: Jeff
authors.initials: J
authors.lastname: Abramson
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D015640:Ion Channel Gating; D008051:Lipid Bilayers / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D009154:Mutation; D016062:Porosity; D015202:Protein Engineering; D017433:Protein Structure, Secondary; D050995:Voltage-Dependent Anion Channel 1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D008051:Lipid Bilayers; D050995:Voltage-Dependent Anion Channel 1