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, deepetch 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 $3 and $2; the triads associate with $1. 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. © 1985, Rockefeller University Press., All rights reserved.