Figure 16-44. Ciliary dynein.

Figure 16-44Ciliary dynein

Ciliary dynein is a large protein assembly (nearly 2 million daltons) composed of 9 to 12 polypeptide chains, the largest of which is the heavy chain of 512,000 daltons. (A) The heavy chains are believed to form the major portion of the globular head and stem domains, and many of the smaller chains are clustered around the base of the stem. The base of the molecule binds tightly to an A microtubule in an ATP-independent manner, while the large globular heads have an ATP-dependent-binding site for a B microtubule (see Figure 16-41). When the heads hydrolyze their bound ATP, they move toward the minus end of this second microtubule, thereby producing a sliding force between the adjacent microtubule doublets in a cilium or flagellum (see Figure 16-43). The three-headed form of ciliary dynein, formed from three heavy chains, is illustrated here. (B) Freeze-etch electron micrograph of a cilium showing the dynein arms projecting at regular intervals from the doublet microtubules. (B, courtesy of John Heuser.)

From: Cilia and Centrioles

Cover of Molecular Biology of the Cell
Molecular Biology of the Cell. 3rd edition.
Alberts B, Bray D, Lewis J, et al.
New York: Garland Science; 1994.
Copyright © 1994, Bruce Alberts, Dennis Bray, Julian Lewis, Martin Raff, Keith Roberts, and James D Watson.

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