title: Selective contrast in electron microscopy of crystalline cytochrome oxidase.
abstract: We have used various techniques for preparation of specimens for electron microscopy in order to selectively contrast different regions of vesicle crystals of cytochrome c oxidase dimers. The results are consistent with a dimer composed of two y-shaped monomers [Fuller et al., J. Mol. Biol. 134 (1979) 305] aligned along one pair of arms with the other pair of arms approximately 70 A apart. The four arms of the monomers lie within and perpendicular to the lipid bilayer in which the dimer is embedded, and the arms protrude approximately 25 A from the lipid bilayer on the matrix side of the membrane. The cytoplasmic side domains of the two monomers split away from one another forming a large cleft in the dimer. Monovalent antibodies (Fab fragments) to subunit IV appear to bind to the two monomer arms which are closely apposed across the two-fold axis of the dimer.
mesh_terms: D003461:Crystallography / Q000379:methods*; D003576:Electron Transport Complex IV; D005614:Freeze Fracturing; D007140:Immunoglobulin Fab Fragments; D007158:Immunologic Techniques; D007425:Intracellular Membranes / Q000648:ultrastructure; D046911:Macromolecular Substances; D008563:Membrane Lipids; D008565:Membrane Proteins; D008854:Microscopy, Electron / Q000379:methods*; D008928:Mitochondria / Q000648:ultrastructure; D011487:Protein Conformation
chemical_list: D007140:Immunoglobulin Fab Fragments; D046911:Macromolecular Substances; D008563:Membrane Lipids; D008565:Membrane Proteins; D003576:Electron Transport Complex IV