The Journal of Cell Biology, Vol 72, 278-291, Copyright © 1977 by The Rockefeller University Press
Thermotropic lateral translational motion of intramembrane particles in the inner mitochondrial membrane and its inhibition by artificial peripheral proteins
M Hochli and CR Hackenbrock
Freeze fracturing and deep etching have been used to study thermotropic
lateral translational motion of intramembrane particles and membrane
surface anionic groups in the inner mitochondrial membrane. When the inner
membrane is equilibrated at low temperature, the fracture faces of both
halves of the membrane reveal a lateral separation between intramembrane
particles and particle free, large smooth patches. Such separation is
completely reversed through free lateral translational diffusion by
reversing the temperature. The low temperature induced, particle-free,
smooth membrane patches appear to represent regions of protein-excluding,
ordered bilayer lipid which form during thermotropic liquid crystalline to
gel state phase transitions. When polycationic ferritin is
electrostatically bound to anionic groups exposed at the membrane surface
at concentrations which inhibit the activities of cytochrome c oxidase and
succinate permease, the bound ferritin migrates with intramembrane
particles during the thermotropic lateral separation between the membrane
particles and smooth patches. When bound polycationic ferritin is
cross-bridged with native ferritin, an artificial peripheral protein
lattice forms in association with the surface anionic groups and diminishes
the thermotropic lateral translational motion of intramembrane particles in
the membrane. These results reveal that the anionic groups of metabolically
active integral proteins which are known to be exposed at the surface of
the inner mitochondrial membrane migrate with intramembrane particles in
the plane of the membrane under conditions which induce lipid-protein
lateral separations. In addition, cross-bridging of the anionic groups
through an artificial peripheral protein lattice appears to diminish such
induced lipid protein lateral separations.