Stable intermicrotubule linkers in the isolated cytostomal apparatus of Tetramitus

Abstract

Detergent lysis of Tetramitus rostratus flagellates liberates intact a "cytostomal apparatus" composed of four flagella, their basal bodies, and several striated flagellar rootlets, as well as an unusually stable array of long cytoskeletal microtubules. Cytostomal apparatuses, purified on 5–15% Ficoll gradients and negatively stained with uranyl acetate, reveal abundant arrays of intermicrotubule linkers (IMTLs). These linkers, which are irregularly spaced vertically at approximately 50-nm intervals, appear to limit intermicrotubule distances to about 120 nm. The IMTLs of Tetramitus are unusually long, unusually abundant, and unusually stable: it is speculated that they represent an exaggerated form of (and hence a means to identify) a universal component of the microtrabecular lattice of eukaryote cells.