Three-dimensional structure of basal body triplet revealed by electron cryo-tomography |
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Authors: | Li Sam Fernandez Jose-Jesus Marshall Wallace F Agard David A |
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Institution: | The Howard Hughes Medical Institute, University of California, San Francisco, CA 94158-2517, USA. |
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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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Keywords: | basal body centriole Chlamydomonas reinhardtii electron cryo‐tomography three‐dimensional reconstruction |
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