Functional interaction betweenChlamydomonas outer arm dynein subunits: The γ subunit suppresses the ATPase activity of the αβ dimer
✍ Scribed by Nakamura, Ken-ichi ;Wilkerson, Curtis G. ;Witman, George B.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 134 KB
- Volume
- 37
- Category
- Article
- ISSN
- 0886-1544
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✦ Synopsis
The ab dimer and the g subunit of the Chlamydomonas outer arm dynein were solubilized by treating isolated axonemes with 0.6 M KCl, and purified by sucrose density gradient centrifugation. The axonemes were from an ida1 mutant to eliminate contamination of outer arm subunits by inner arm dynein I1, and the axonemes were pre-extracted with 0.6 M CH 3 COOK to remove non-dynein protein that might otherwise contaminate outer arm dynein fractions in the sucrose gradient. In addition, purer fractions of outer arm dynein subunits were obtained by modifying the centrifugation conditions to take advantage of the propensity of the dynein to dissociate under high hydrostatic pressure in the presence of Mg 21 . When sucrose gradient fractions containing the g subunit were added to a fraction containing the purified ab dimer under conditions expected to promote reassociation of the subunits to form a trimeric outer arm dynein complex [Takada et al., 1992: J. Biochem. 111:758-762], the total ATPase activity of the mixture was suppressed to a level lower than that of the original ab dimer fraction. The inhibition paralleled the distribution of g subunit in the sucrose gradient, was saturable, and was maximum at an approximately equimolar ratio of the g subunit to the ab dimer. These results indicate that when the g subunit interacts with the ab dimer, the latter's ATPase activity is modulated downward. Previous results showed that interaction of the a subunit with the b subunit suppressed the b subunit's ATPase activity