The long-range goal of this research is to understand how the structure of the mitochondrial outer membrane relates to its biological functions. Attention is focused on the voltage- dependent anion-selective channels (VDAC) which determine the permeability of this membrane to polar molecules and ions. Electron microscopy and image analysis will be used to determine the three-dimensional structure of the fungal and yeast VDAC channels in unstained, frozen-hydrated planar crystals. By comparing the structures of normal channels, channels treated with different effectors, and genetically altered channels, insights may be obtained into the molecular mechanisms underlying the channel's functions. In addition, the interactions of the VDAC channel with known and putative protein ligands (hexokinase, import proteins) will be studied by the same techniques. The results of electron crystallography will be supplemented with data from x-ray diffraction and circular dichroism, as well as from amino- acid sequence analyses, to determine the secondary structure of the channel protein.
