Purification and Characterization of Outer Arm Dynein from Trypanosoma brucei

Abstract

converted into complex waveforms. The conversion mechanism has remained a long-standing unresolved issue. Since Chlamydomonas flagella change their waveforms from a flagellar type to a ciliary type, responding to the increase in intracellular Ca 2þ concentrations, this response may provide a hint for the mechanism of the flagellar waveform generation. To provides the spatial arrangement of axonemal components on doublet microtubules of Chlamydomonas under different Ca 2þ concentrations and the change in the helical arrangement of these components, we carried out the small-angle X-ray fiber diffraction. The axonemes were oriented in a physiological solution by continuous shear-flow and were exposed to intense and stable X-rays in the synchrotron radiation facility SPring-8 BL40XU. The diffraction patterns showed the layer lines of the radial-spokeoriginating 48-nm and dynein-arm originating 24-nm reflections at the low Ca 2þ concentrations while they decreased their intensities in the high Ca 2þ concentrations, suggesting the change in the helical symmetry of the doublets of the axoneme. The relation between the helical symmetry and the flagella waveform change was examined by a numerical model. In this model, the change of the helical symmetry was incorporated as a positional shift of the antagonistic motor pairs. The simulation showed that the amplitude/frequency of the flagellar beating varies with the shift of the motors. It was also found that the effect of the shift increases the asymmetry of the flagellar beat when the axonemal structure was considered to be asymmetric. This work was supported by JSPS KAKENHI(26440089, 17K07376, JP16H06280, the Takeda Science Foundation (K.O).