title: Three-dimensional structure of basal body triplet revealed by electron cryo-tomography.
abstract: Basal bodies and centrioles play central roles in microtubule (MT)-organizing centres within many eukaryotes. They share a barrel-shaped cylindrical structure composed of nine MT triplet blades. Here, we report the structure of the basal body triplet at 33 Å resolution obtained by electron cryo-tomography and 3D subtomogram averaging. By fitting the atomic structure of tubulin into the EM density, we built a pseudo-atomic model of the tubulin protofilaments at the core of the triplet. The 3D density map reveals additional densities that represent non-tubulin proteins attached to the triplet, including a large inner circular structure in the basal body lumen, which functions as a scaffold to stabilize the entire basal body barrel. We found clear longitudinal structural variations along the basal body, suggesting a sequential and coordinated assembly mechanism. We propose a model in which δ-tubulin and other components participate in the assembly of the basal body.
authors.affiliation: The Howard Hughes Medical Institute, University of California, San Francisco, CA 94158-2517, USA.
authors.forename: Sam
authors.initials: S
authors.lastname: Li
authors.forename: Jose-Jesus
authors.initials: JJ
authors.lastname: Fernandez
authors.forename: Wallace F
authors.initials: WF
authors.lastname: Marshall
authors.forename: David A
authors.initials: DA
authors.lastname: Agard
mesh_terms: D055032:Electron Microscope Tomography / Q000379:methods*; D008870:Microtubules / Q000648:ultrastructure*; D008958:Models, Molecular; D015394:Molecular Structure