Observations on the molecular components stabilizing the microtubular system of the marginal band in the newt erythrocyte

Microtubules have been classified as either stable or labile, according to their resistance towards depolymerizing agents. The highest stability belongs to those organized in composite structures, in which many other proteins are associated with the tubulin. Among these microtubular systems, the marginal band of amphibian erythrocytes is unusually stable. This system can be readily isolated from Triturus red blood cells, and therefore lends itself very readily to ultrastructural and biochemical analyses. Immunofluorescence and electrophoretic analyses of the isolated bands reveal 14 components, among which tubulin, actin, myosin and a 90K glycoprotein were identified. Tannic acid-glutaraldehyde fixation reveals a conspicuous opaque material surrounding the microtubules. Cationized ferritin binding suggests the presence of anionic sites. Moreover, neuraminidase causes the disorganization of the microtubule-associated opaque material. The 90K glycoprotein is presumed to be related to the unusual stability of the microtubular system forming the marginal band.