Filaments Associated With the Human Erythrocyte Membrane: A Scanning Electron Microscope Study

A reticulum of filaments covering the cytoplasmic surface of human erythrocyte membranes was visualized at a resolution of 50-100 Å using a scanning electron microscope. This network was visible in ghosts split or torn open to reveal their interior space; in Triton X-100 extracted ghost residues; and even in intact cells, where the contour of the outer surfaces appeared to reflect an underlying meshwork. In addition to filaments, annular figures and nodes were seen in the reticulum. Since the Triton X-100 extraction leaves insoluble a residue that is predominantly spectrin and actin, the residues observed may be assumed to be composed of these proteins. Also, since the reticulum seen inside ghosts appears morphologically similar to the Triton residue reticulum, it may be tentatively concluded that this, too, is made up of spectrin and actin.