4 ATP-BINDING SITES IN THE MIDREGION OF THE BETA-HEAVY CHAIN OF DYNEIN

THE 'motor' proteins of eukaryotic cells contain specialized domains that hydrolyse ATP to produce force and movement along a cytoskeletal polymer (actin in the case of the myosin family; microtubules in the case of the kinesin family and dyneins). There are motor-protein superfamilies in which each member has a conserved force-generating domain joined to a different 'tail' which conveys specific attachment properties (see ref. 1 for a review). The minus-end-directed microtubule motors, the dyneins 2, may also constitute a superfamily of force-generating proteins with distinct attachment domains 3. Axonemal outer-arm dynein from sea urchin spermatozoa is a multimeric protein consisting of two heavy chains (alpha and beta) with ATPase activity. three intermediate chains and several light chains 4. Here I report the sequence of cloned complementary DNA encoding the beta-heavy chain of a dynein motor molecule. The predicted amino-acid sequence reveals four ATP-binding consensus sequences in the central domain. The dynein beta-heavy chain is thought to associate transiently with a microtubule during ATP hydrolysis 5, but the ATP-dependent microtubule-binding sequence common to the kinesin superfamily is not found in the dynein beta-heavy chain. These unique features distinguish the dynein beta-heavy chain from other motor protein superfamilies and may be characteristic of the dynein superfamily.