Immunoreactive Forms of Human Erythrocyte Ankyrin Are Localized in Mitotic Structures in Cultured Cells and Are Associated with Microtubules in Brain

The mechanism of linkage of cell membranes to structural and regulatory proteins in the cytoplasm is a major unsolved problem with implications for many areas of cell biology. The motion and topography of membrane-spanning cell-surface proteins are thought to be controlled by associations with cytoplasmic proteins on the inner surface of the plasma membrane. Membrane-protein linkages also most likely provide the necessary fixed points for converting into useful work the mechanical stress produced by contractile proteins and thus are essential for muscle contraction, cytokinesis, cell motility, and attachment of cells to surfaces. It is also likely that the complex morphology of membrane systems, such as the endoplasmic reticulum and the plasma membrane with its ruffles and microvillar extensions, requires associated structural proteins in addition to a simple lipid bilayer with integral proteins.