Structure of the mitochondrial outer membrane channel derived from electron microscopy of 2D crystals

1989 ◽  
Vol 21 (4) ◽  
pp. 427-437 ◽  
Author(s):  
Carmen A. Mannella
Keyword(s):  
Electron Microscopy ◽  
Outer Membrane ◽  
Mitochondrial Outer Membrane ◽  
Membrane Channel ◽  
Outer Membrane Channel ◽  
2D Crystals

Cryo-Electron Microscopy and Correlation Averaging of Frozen-Hydrated, Polymorphic 2D Crystals of the Mitochondrial Outer Membrane Channel

1990 ◽  
Vol 48 (1) ◽  
pp. 100-101
Author(s):  
Xiao-Wei Guo
Keyword(s):  
Outer Membrane ◽  
Hexagonal Lattice ◽  
Mitochondrial Outer Membrane ◽  
Rectangular Lattice ◽  
Electron Microscopic ◽  
Cryo Electron Microscopy ◽  
Voltage Dependent ◽  
Outer Membrane Channel ◽  
2D Crystals ◽  
Vdac Channel

Voltage-dependent, anion-selective channels (VDAC) are formed in the mitochondrial outer membrane (mitOM) by a 30-kDa polypeptide. These channels form ordered 2D arrays when mitOMs from Neurospora crassa are treated with soluble phospholipase A2. We obtain low-dose electron microscopic images of unstained specimens of VDAC crystals preserved in vitreous ice, using a Philips EM420 equipped with a Gatan cryo-transfer stage. We then use correlation analysis to compute average projections of the channel crystals. The procedure involves Fourier-filtration of a region within a crystal field to obtain a preliminary average that is subsequently cross-correlated with the entire crystal. Subregions are windowed from the crystal image at coordinates of peaks in the cross-correlation function (CCF, see Figures 1 and 2) and summed to form averages (Figure 3).The VDAC channel forms several different types of crystalline arrays in mitOMs. The polymorph first observed during phospholipase treatment is a parallelogram array (a=13 run, b=11.5 run, θ==109°) containing 6 water-filled pores per unit cell. Figure 1 shows the CCF of a sub-field of such an “oblique” array used to compute the correlation average of Figure 3A. With increased phospholipase treatment, other polymorphs are observed, often co-existing within the same crystal. For example, two distinct (but closely related) types of lattices occur in the field corresponding to the CCF of Figure 2: a “contracted” version of the parallelogram lattice (a=13 run, b=10 run, θ=99°), and a near-rectangular lattice (a=8.5 run, b=5 nm). The pattern of maxima in this CCF suggests that a third, near-hexagonal lattice (a=4.5 nm) may also be present. The correlation averages of Figures 3B-D were computed from polycrystalline fields, using peak coordinates in regions of CCFs corresponding to each of the three lattice types.

scholarly journals Bacterial Expression and Characterization of the Mitochondrial Outer Membrane Channel

1998 ◽  
Vol 273 (22) ◽  
pp. 13794-13800 ◽  
Author(s):  
Daniel A. Koppel ◽  
Kathleen W. Kinnally ◽  
Paul Masters ◽  
Michael Forte ◽  
Elizabeth Blachly-Dyson ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Bacterial Expression ◽  
Mitochondrial Outer Membrane ◽  
Membrane Channel ◽  
Outer Membrane Channel

Voltage gating of the mitochondrial outer membrane channel VDAC is regulated by a very conserved protein

1991 ◽  
Vol 260 (2) ◽  
pp. C371-C374 ◽  
Author(s):  
M. Y. Liu ◽  
M. Colombini
Keyword(s):  
Outer Membrane ◽  
Physiological Role ◽  
Mitochondrial Outer Membrane ◽  
Voltage Sensitivity ◽  
Membrane Channel ◽  
Mitochondrial Fractions ◽  
Voltage Dependent ◽  
Outer Membrane Channel ◽  
Vdac Channels ◽  
Closing Rate

Soluble protein preparations obtained from the mitochondrial fractions of three very different organisms, Neurospora crassa, rat, and potato, were discovered to greatly enhance the voltage sensitivity of the mitochondrial outer membrane channel, VDAC. The active ingredient, referred to as the VDAC modulator, increased the rate of voltage-dependent channel closure by approximately 10-fold. The modulator from one species increased the closing rate of VDAC channels from all three species. The activity is pronase sensitive and not mimicked by another negatively charged protein, BSA. The highly conserved property of this modulator suggests an important physiological role in regulating mitochondrial function.

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