title: Distinct roles of 1alpha and 1beta heavy chains of the inner arm dynein I1 of Chlamydomonas flagella.
abstract: 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 1α or 1β motor domain to distinguish the functional role of each motor domain. Single- particle electronic microscopic analysis confirmed that both the I1α and I1β complexes are single headed with similar ringlike, motor domain structures. Despite similarity in structure, however, the I1β complex has severalfold higher ATPase activity and microtubule gliding motility compared to the I1α complex. Moreover, in vivo measurement of microtubule sliding in axonemes revealed that the loss of the 1β 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 I1β motor domain is an effective motor required for wild-type microtubule sliding, whereas the I1α motor domain may be responsible for local restraint of microtubule sliding.
authors.affiliation: Kobe Advanced ICT Research Center, National Institute of Information and Communications Technology, Kobe, Japan.
authors.forename: Shiori
authors.initials: S
authors.lastname: Toba
authors.forename: Laura A
authors.initials: LA
authors.lastname: Fox
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sakakibara
authors.forename: Mary E
authors.initials: ME
authors.lastname: Porter
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Oiwa
authors.forename: Winfield S
authors.initials: WS
authors.lastname: Sale
mesh_terms: D054468:Axoneme / Q000378:metabolism*; D002696:Chlamydomonas / Q000235:genetics / Q000378:metabolism*; D004398:Dyneins / Q000737:chemistry / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D005407:Flagella / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D010766:Phosphorylation; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D017434:Protein Structure, Tertiary
chemical_list: D010940:Plant Proteins; D004398:Dyneins