AXONEMES PARALYZED BY THE PRESENCE OF DYNEINS UNABLE TO USE RIBOSE-MODIFIED ATP

Substrate analogs are useful for studying the structures of active sit es and for distinguishing between similar enzyme activities. Fluoresce nt ribose-modified ATP analogs were used to investigate the functional differences between dynein ATPases. These analogs reactivate (support the movement of) sea urchin sperm axonemes, yet they do not reactivat e wild-type Chlamydomonas axonemes. Surprisingly, the analogs reactiva te the axonemes of mutants completely missing the outer arm dyneins. C ompetition experiments using ATP and these analogs provide strong evid ence that the analogs bind to all dynein active sites but fail to rele ase a subset of dyneins from rigor. We suggest that this subset of Chl amydomonas outer arm dyneins unable to use the analogs remains in rigo r in the presence of the analogs and paralyzes the axoneme. (C) 1994 W iley-Liss, Inc.