Sea urchin dyneins
Abstract
Dynein is a large, complex microtubule mechanochemical translocator. Although discovered over 25 years ago in the axonemes of protozoa and sea urchin sperm flagella, relatively little is known about the structure and function of this important motor molecule that powers active microtubule sliding in cilia and flagella, mediates axonal transport and potentially is involved in other forms of cytoplasmic-based microtubule motility. The goal of this investigation has centered on the characterization and comparison of the dyneins within a single organism, the sea urchin, as a means to understand subtle structure-function relationships of dynein. Biochemical, immunological and molecular methods have been employed to this end. Particular emphasis has been placed upon the study of the large heavy chains (ca. Mr 450K each) which contain the microtubule-binding and MgATPase activities. The sea urchin unfertilized egg contains at least one dynein, the function of which heretofore has been unknown. In addition, blastula stage embryos become ciliated and offer the chance to compare a ciliary dynein with that of a second axonemal dynein found in the sea urchin sperm flagellum. The dyneins from these three sources have been characterized and compared in terms of their subunit compositions, enzymatic activities and basic structural properties of the heavy chains. The role of the dynein stored in the unfertilized egg has been determined and, finally, the developmental expression and use of the dyneins in embryonic development has been investigated. As a result of these studies, well-characterized anti-dynein sera, a set of overlapping cDNA clones encoding a portion of the carboxyl-terminus of the dynein $\beta$ heavy chain and a reasonable idea of the compositions of the three dynein complexes are now in hand. The sea urchin makes use of at least two distinct dyneins in the flagellar and ciliary axonemes. Although similar, the two axonemal dyneins are distinguishable immunologically and biochemically. The first primary sequence data for a dynein $\beta$ heavy chain also is presented. Further, it appears that the stored 20S egg dynein is a ciliary dynein precursor that is processed prior to or during ciliogenesis. Finally, the basic pattern of expression of the dynein heavy chains during embryogenesis and ciliary regeneration has been determined.
Degree
Ph.D.
Advisors
Asai, Purdue University.
Subject Area
Biology|Aquaculture|Fish production
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