BIOCHEMICAL-ANALYSIS OF A MUTANT TETRAHYMENA LACKING OUTER DYNEIN ARMS

Tetrahymena thermophila mutants homozygous for the oad mutation become nonmotile when grown at the restrictive temperature, and axonemes iso lated from nonmotile mutants lack approximately 90% of their outer dyn ein arms. Electrophoretic analyses of axonemes isolated from nonmotile mutants (oad axonemes) indicate they contain significantly fewer of t he 22 S dynein heavy chains that axonemes isolated from wild-type cell s (wild-type axonemes) contain. The 22 S dynein heavy chains that rema in in axonemes isolated from nonmotile, oad mutants are assembled into 22 S dynein particles that exhibit wild-type levels of ATPase activit y. Two-dimensional gel electrophoresis of oad axonemes show that they are deficient in no proteins other than those proteins thought to be c omponents of 22 S dynein. This report is the first formal proof that o uter dynein arms in Tetrahymena cilia are composed of 22 S dynein.