Fig. 4. Electron microscopy
of 2-dimensional crystals of VDAC channels induced in the outer membranes
of N. crassa mitochondria by slow phospholipase
treatment. Both figures have been computer filtered
and averaged with respect to the 6-channel repeating unit. The upper panel
shows a surface view obtained by
freeze-drying and shadowing these crystals (courtesy
of Lorie Thomas). The openings of the channels are seen as dark depressions.
The lower figure shows the
crystals after freezing in a thin layer of vitreous
ice (courtesy of Carmen Mannella). The white areas are the channel lumens
and the dark areas are the protein
structures. The circle indicates the center of
a location surrounded by 6 channels. This location corresponds to the elevated
(white) region in the upper panel.