The contractile axostyle is a ribbon-shaped organelle present in certain species of flagellates found in the hindgut of wood eating insects. This organelle propagates an undulatory wave whose motion, like flagella and cilia, is related to microtubules. Unlike the axoneme of cilia and flagella, however, the axostyle is composed of singlet microtubules linked together in parallel rows. Axostyles were isolated from Cryptocercus gut protozoa with Triton X-100. Normal motility of the isolated axostyle could be restored with adenosine triphosphate (ATP); the specific conditions necessary for this reactivation were essentially identical with those reported for the reactivation of isolated flagella or whole sperm. ATPase activity of the isolated axostyle was comparable to the values reported for ciliary or flagellar axonemes. The axostyle was reasonably specific for ATP. Most of the proteins of the isolated axostyle comigrated with proteins of the ciliary axoneme on sodium dodecyl sulfate (SDS) polyacrylamide gels (i e. equivalent molecular weights). These included the following: the higher molecular weight component of dynein, tubulin, linkage protein (nexin), and various secondary proteins. Evidence for dynein in the axostyle is presented and a model proposed to explain how repeated propagated waves can be generated.

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