Asymmetric mass distribution of (Na+ + K+)-ATPase in membranes studied by freeze-fracture-etch electron microscopy

Particles and pits matched in native membranes

“…Most of the particles remain on one fracture face while the complementary pits appear on the opposite fracture face. Since in a randomly sealed population of microsomal vesicles (Ting-Beall et al, 1984), particles can appear exclusively on either concave or convex fracture faces, and since particles are associated with the PF face, it is reasonable to assume that areas 2 and 3 are the P F faces, whereas areas 1 and 4 are pitted EF faces. Occasionally IMPS are found on the E F face (Fig.…”

“…In our previous FFE studies (Ting-Beall et al, 1984) and. more recently with complementary replicas of right-side-out sealed microsomal vesicles (unpublished data), we have shown that randomly distributed intramembrane particles appear on the protoplasmic fracture (PF) faces, and pits appear on the external fracture (EF) faces but without convincing extended complementarity.…”

“…The location, asymmetric orientation, and mass distribution of Na+,K+-ATPase in membranes have been shown by biochemical (Whittam & Ager, 1964;Perrone & Blostein, 1973), immunochemical (Ruoho & Kyte, 1974;Kyte, 1975) and morphological (Ting-Beall et al, 1984;Zampighi et al, 1984) studies. In our previous FFE studies (Ting-Beall et al, 1984) and. more recently with complementary replicas of right-side-out sealed microsomal vesicles (unpublished data), we have shown that randomly distributed intramembrane particles appear on the protoplasmic fracture (PF) faces, and pits appear on the external fracture (EF) faces but without convincing extended complementarity.…”

“…The location, asymmetric orientation, and mass distribution of Na+,K+-ATPase in membranes have been shown by biochemical (Whittam & Ager, 1964;Perrone & Blostein, 1973), immunochemical (Ruoho & Kyte, 1974;Kyte, 1975) and morphological (Ting-Beall et al, 1984;Zampighi et al, 1984) studies. In our previous FFE studies (Ting-Beall et al, 1984) and.…”

The receptor function of the Na+, K+-activated adenosine triphosphatase system

“…227 cytoplasmic protrusion of the a-subunit on a 60kDa C-terminal tryptic fragment (Karlish, 1980;J0rgensen et al, 1982) and may well be 2-3 nm away from the internal surface of the bilayer. In contrast, the protein protrusion on the extracellular side of the membrane is small (Ting-Beall et al, 1984;Zampighi et al, 1984) so that the receptor site is probably close to the lipid bilayer surface. That lipids could be a component of the receptor site, in analogy to opiate and cholera toxin receptors (Brady & Fishman, 1979;Lee & Smith, 1980;Deber & Behnam, 1984), is suggested by (i) the slower K+-induced release of lipophilic cardioactive steroids compared with that of more hydrophilic compounds (Akera et al, 1979); (ii) the lipid-specific modulation of the receptor sensitivity (Abeywardena & Charnock, 1983); and (iii) a postulated role of sulphatides in the K+ and ouabain binding sites at the cell surface (Karlsson, 1976;Gonzales & Zambrano, 1983).…”