title: Substructure of inner dynein arms, radial spokes, and the central pair/projection complex of cilia and flagella.
abstract: The substructure of the components of the axoneme interior--the inner dynein arms, the radial spokes, and the central pair/projection complex--was analyzed for Chlamydomonas. Tetrahymena, Strongelocentrotus, and Mnemiopsis using the quick-freeze, deep-etch technique. The inner arms are shown to resemble the outer arms in overall molecular organization, but they are disposed differently on the microtubule and have two distinct morphologies--dyads with two heads and triads with three. The dyads associate with spokes S3 and S2; the triads associate with S1. The spokes form a three-start right-handed helix with a 288-nm rise; the central pair makes a shallow left-handed twist. The spoke heads are shown to be made up of four major subunits; two bind to the spoke shaft and two bind to a pair of central-sheath projections.
authors.forename: U W
authors.initials: UW
authors.lastname: Goodenough
authors.forename: J E
authors.initials: JE
authors.lastname: Heuser
mesh_terms: D000818:Animals; D002696:Chlamydomonas / Q000648:ultrastructure; D002923:Cilia / Q000648:ultrastructure*; D003063:Cnidaria; D005407:Flagella / Q000648:ultrastructure*; D005613:Freeze Etching; D008854:Microscopy, Electron; D008870:Microtubules / Q000648:ultrastructure; D012617:Sea Urchins / Q000648:ultrastructure; D013768:Tetrahymena / Q000648:ultrastructure