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MOM were puriied from yeast as previously described 58 and adsorbed
on clean mica surfaces. In medium resolution topographs, corrugated VDAC-
containing membrane areas were easily distinguished from the smoother,
lipid bilayer regions, allowing the estimation of pore packing densities. 59
Mixed domains contained VDAC pores at low (~20%) density; in other
regions the pores were packed at high (~80%) density ( Fig. 2.6a,b ) . Single
VDAC molecules were imaged with characteristic pore dimensions of 3.8 ×
2.7 nm and were ~2 nm in measured depth.
(a)
(b)
Figure 2.6. Supramolecular organization of VDAC in the mitochondrial outer
membranes. (a) Supramolecular organization of VDAC channels. High-density
region on the left and low-density region on the right with some protein “islands” of
variable size, ranging from two to about twenty VDAC (outlines). (b) High-resolution
AFM analysis of densely packed region of VDAC (pore dimensions 3.8 x 2.7 nm;
pore depth ~2 nm).
The obtained results were in line with previously suggested mechanisms
of VDAC's channel regulation that links VDAC's functionality to its membrane
surface density. 58 High mobility of VDAC groups in the observed low-density
mixed domains ( Fig. 2.6a ) could trigger VDAC association in the densely
packed domains and thereby act as a regulator of VDAC activity on the
cellular level. Such an association-dissociation equilibrium is a simple way
of modulating channelling activity. It also points towards possible ways to
control VDAC activity with eventual pharmaceutical agents modifying the
oligomerization properties of VDAC molecules.
2.4.2 Inner Mitochondrial Membranes: Rows of ATP Synthase
Dimers
The ATP synthase functions as a nanometric rotary machine that employs
a transmembrane electrochemical gradient to produce ATP. 60 In spite of
 
 
 
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