Flagellar axonemes that lack the outer dynein arms and a part of the inner dynein arms were prepared by extracting demembranated axonemes of an outer-arm less mutant of Chlamydomonas with a solution containing 0.3 M KC1 and 10 μM ATP. When reactivated with 1 mM ATP, the extracted axonemes, whose beat frequency before the extraction had been 26.9±2.6 Hz (26°C, n=10), beat with a reduced frequency of 14.9±3.7 Hz (26°C, n=10). The decrease in beat frequency depended on the KC1 concentration and on the presence of ATP in the extracting solution. The bend angle and the curvature of bend were not affected by the extraction. Electron microscopic observation showed that 28.5% of the inner arms were weak in appearance or lost in the extracted axoneme. Electrophoresis of the axonemal proteins indicated that one of the high molecular weight polypeptides of the inner dynein arm was reduced in quantity. These results suggest that some part of the inner arms has the function of increasing the flagellar beat frequency but is not essential for flagellar motility.
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