Three-dimensional structure of basal body triplet revealed by electron cryo-tomography.

The Howard Hughes Medical Institute, University of California, San Francisco, CA 94158-2517, USA.
The EMBO Journal (Impact Factor: 10.75). 12/2011; 31(3):552-62. DOI: 10.1038/emboj.2011.460
Source: PubMed

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.

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Wallace Marshall