Membrane Crystals of Ubiquinone: Cytochrome C Reductase from Neurospora Mitochondria

Abstract

Structural Studies on crystalline membrane proteins such as purple membrane (Unwin and Henderson, 1975) and cytochrome oxidase (Frey at al., 1978; Henderson et al., 1977) have shown that these specimens are well suited for high resolution electron microscopy. Since hydrophobic proteins are difficult to study by conventional X-ray crystallography, it is clearly important to be able to obtain structural information from electron microscopy, and therefore to develop methods for preparing well-ordered, extensive sheets of purified membrane proteins. We describe here a procedure for crystallising a detergent-solubilised, highly purified mitochondrial membrane protein, cytochrome c reductase, in vesicles formed from lipid mixtures, and give some of the preliminary electron microscopy results.