title: Lipid dynamics and protein-lipid interactions in 2D crystals formed with the β-barrel integral membrane protein VDAC1.
abstract: We employ a combination of (13)C/(15)N magic angle spinning (MAS) NMR and (2)H NMR to study the structural and functional consequences of different membrane environments on VDAC1 and, conversely, the effect of VDAC1 on the structure of the lipid bilayer. MAS spectra reveal a well-structured VDAC1 in 2D crystals of dimyristoylphosphatidylcholine (DMPC) and diphytanoylphosphatidylcholine (DPhPC), and their temperature dependence suggests that the VDAC structure does not change conformation above and below the lipid phase transition temperature. The same data show that the N-terminus remains structured at both low and high temperatures. Importantly, functional studies based on electrophysiological measurements on these same samples show fully functional channels, even without the presence of Triton X-100 that has been found necessary for in vitro-refolded channels. (2)H solid-state NMR and differential scanning calorimetry were used to investigate the dynamics and phase behavior of the lipids within the VDAC1 2D crystals. (2)H NMR spectra indicate that the presence of protein in DMPC results in a broad lipid phase transition that is shifted from 19 to ~27 °C and show the existence of different lipid populations, consistent with the presence of both annular and bulk lipids in the functionally and structurally homogeneous samples.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Eddy
authors.forename: Ta-Chung
authors.initials: TC
authors.lastname: Ong
authors.forename: Lindsay
authors.initials: L
authors.lastname: Clark
authors.forename: Oscar
authors.initials: O
authors.lastname: Teijido
authors.forename: Patrick C A
authors.initials: PC
authors.lastname: van der Wel
authors.forename: Robert
authors.initials: R
authors.lastname: Garces
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wagner
authors.forename: Tatiana K
authors.initials: TK
authors.lastname: Rostovtseva
authors.forename: Robert G
authors.initials: RG
authors.lastname: Griffin
mesh_terms: D002152:Calorimetry, Differential Scanning / Q000379:methods; D003460:Crystallization; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D004594:Electrophysiology / Q000379:methods; D006801:Humans; D008051:Lipid Bilayers; D008055:Lipids / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008565:Membrane Proteins / Q000737:chemistry; D017830:Octoxynol / Q000494:pharmacology; D010713:Phosphatidylcholines / Q000737:chemistry; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D050995:Voltage-Dependent Anion Channel 1 / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D008055:Lipids; D008565:Membrane Proteins; D010713:Phosphatidylcholines; C494762:VDAC1 protein, human; C021016:1,2-diphytanoylphosphatidylcholine; D017830:Octoxynol; D050995:Voltage-Dependent Anion Channel 1; D004134:Dimyristoylphosphatidylcholine