| Budget Amount *help |
¥6,200,000 (Direct Cost: ¥6,200,000)
Fiscal Year 1993: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1992: ¥4,900,000 (Direct Cost: ¥4,900,000)
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| Research Abstract |
Dynein plays a most important function in the flagellar beating mechanism. Flagellar dynein comprises as many as ten different heavy chains in the inner and outer arms, but the specific function of each heavy chain is unknown. To approach the function of various heavy chains, we carried out two lines of experiments : isolation Chlamydomonas mutants that lack particular heavy chains, and assay of the motile activity of isolated heavy chains.
In the first approach, we isolated a mutant that lacks part of the beta heavy chain of the outer arm and two kinds of mutants that lack different sets of inner-arm heavy chains. Studies on these mutants have indicated that (1) the beta heavy chain is more important than the alpha heavy chain in the function of outer arm dynein, and (2) five out of the eight known inner-arm heavy chains are unnecessary for the generation of flagellar beating.
In the second line of study, we first developed a system in which dissociated outer-arm dynein, an alpha/beta subparticle and a gamma subparticle, can be recombined and attached to an outer arm-less mutant, oda1. This study again demonstrated that the beta heavy chain is important in the outer arm function. Finally, we developed an in vitro motility assay system using isolated inner arm dynein subspecies. Six out of the seven subspecies (containing eight heavy chains) were found to have activities to translocate microtubules in vitro. Different subspecies differ in maximal velocity and in the ability to cause microtubule rotation. These studies indicate that the flagella contain various dyneins that differ functionally. How these different dyneins cooperate in producing regular flagellar beating is a fascinating future problem.
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