Translational Mobility of the Membrane Intercalated Particles of Human Erythrocyte Ghosts

Abstract

This paper demonstrates the translational movement aIong the plane of the human erythrocyte ghost of the membrane particles exposed by freeze-fracture. The membrane particles can be aggregated by incubation of the ghosts in media with a pI-I in the vicinity of 5 5 or 3 5. The particles are disaggregated in neutral and alkaline media (pH 9 5) and also at pH 4.5 Aggregation of the particles at pH 5.5 is reversible, prevented b,z prefixation in glutaraldehyde and by media of high ionic strength. Particle aggregation occurs within 2-4 min. These results are consistent with the concept that the erythrocyte ghost membrane is a planar fluid domain formed by a bilayer membrane continuum which is interrupted by localized, yet mobile, proteic intercalations.

Particle Movements in Chloroplast Membranes: Quantitative Measurements of Membrane Fluidity by the Freeze-Fracture Technique

“…Lateral movements of freeze-fracture particles, presumed to be protein, have been observed in response to environmental pH changes in erythrocyte ghosts (2), during phase transitions in membrane lipids (3), in membrane receptors. during secretion in Tetrahymena (4), in lymphocytes (5), possibly in membranes undergoing pinocytosis (6), and elsewhere, However, quantitative measurements on the translocation of freeze-fracture particles are lacking.…”

Membrane Intercalated Particles in Human Erythrocyte Ghosts: Sites of Preferred Passage of Water Molecules at Low Temperature

“…The surface patterns of meandering canyons and rugosities were strinkingly similar to those displayed by the aggregates of membrane intercalated particles on fracture face A (Fig. 7) caused by incubation at pH 5.5 (10). Proof that the system of canyons and rugosities corresponded to the membrane regions comprised of particle aggregates was obtained by selectively labeling anionic sites at the outer surface regions of the membrane-intercalated particles with a ferritin derivative with high isoelectric point (19); the positively charged label could be exclusively traced onto the system of canyons and reliefs (Figs.…”

“…brane as formed by a bilayer continuum, which is interrupted by stable, yet potentially mobile, proteic intercalations (10,14,15). Freeze-fracture of plasma membranes clearly illustrates these views because it reveals that the bilayer domains of the membrane (split during the fracture process) are interrupted by numerous particulate components (11,16).…”

“…, . r v r - (10). Concentric organization of hydrophilic and hydrophobic spaces is unfavorable because it would result in exposure of hydrophilic regions of the particle to a hydrophobic environment (Ia) or vice-versa (Ib) and, consequently, in entropy reduction.…”

“…potassium phosphate buffer-1 mM CaCl2 at pH 5.5 for 30 min at 300 to aggregate the membrane particles (10). The ghosts were washed twice in a 1: 20 dilution of the buffer and frozen in the liquid phase of partially solidified Freon 22 cooled by liquid nitrogen.…”