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pubmed:abstractText |
The Chlamydomonas I1 dynein is a two-headed inner dynein arm important for the regulation of flagellar bending. Here we took advantage of mutant strains lacking either the 1? or 1? motor domain to distinguish the functional role of each motor domain. Single- particle electronic microscopic analysis confirmed that both the I1? and I1? complexes are single headed with similar ringlike, motor domain structures. Despite similarity in structure, however, the I1? complex has severalfold higher ATPase activity and microtubule gliding motility compared to the I1? complex. Moreover, in vivo measurement of microtubule sliding in axonemes revealed that the loss of the 1? motor results in a more severe impairment in motility and failure in regulation of microtubule sliding by the I1 dynein phosphoregulatory mechanism. The data indicate that each I1 motor domain is distinct in function: The I1? motor domain is an effective motor required for wild-type microtubule sliding, whereas the I1? motor domain may be responsible for local restraint of microtubule sliding.
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