ANALYSES OF 22S DYNEIN BINDING TO TETRAHYMENA AXONEMES LACKING OUTER DYNEIN ARMS

Tetrahymena thermophila mutants homozygous for the oad mutation become nonmotile when grown at the restrictive temperature of 39 degrees C. Axonemes isolated from nonmotile (oad mutants toad 39 degrees C axonem es) lack approximately 90% of their outer dynein arms and are deficien t in 22S dynein. Here we report that oad 39 degrees C axonemes contain 40% of the 22S dynein heavy chains that wild-type axonemes contain an d that oad axonemes do not undergo ATP-induced microtubule sliding in vitro. Wild-type 22S dynein will bind to the outer arm position in oad axonemes and restore ATP-induced microtubule sliding in those axoneme s. Unlike wild-type 22S dynein, oad 22S dynein does not bind to the ou ter arm position in oad axonemes. These data indicate that the oad mut ation affects some component of the outer arm dynein itself rather tha n the outer arm dynein binding site. These data also indicate that oad axonemes can be used to assay outer dynein arm function.