| Popis: |
Publisher Summary This chapter focuses on cytoskeleton formation and function of the marginal band (MB) of microtubules (MTs). It highlights the cytological, ultrastructural, and molecular observations on nonmammalian erythrocytes. The chapter also discusses comparative work on the cytoskeleton of primitive nucleated erythrocytes in developing mammals. All of the mature nucleated erythrocytes of nonmammalian vertebrates contain marginal bands (MBs). The MB is principally a hooplike continuous microtubule (MT) bundle located close to the plasma membrane in the plane of flattening. For erythrocytes of nonmammalian vertebrates, MB thickness in the light microscope and MT number per electron microscopic (EM) cross section are positively correlated with cell size. The MB is flexible both in situ and after isolation—that is, it can bend and twist without breaking. Tubulin is the major molecular component of MBs. Tubulin was found to constitute 1% of total cell protein, with less than one-half in the MB. The assembly of long MTs typical of MBs might be regulated by a tubulin oligomer pool, limiting the nucleation rate and accounting for at least some non-MB tubulin in the cell. |
