Nature 442, 475-478 (27 July 2006) | doi:10.1038/nature04816; Received 6 February 2006; Accepted 21 April 2006; Published online 31 May 2006

Molecular architecture of axonemal microtubule doublets revealed by cryo-electron tomography

Haixin Sui1 and Kenneth H. Downing1

The axoneme, which forms the core of eukaryotic flagella and cilia, is one of the largest macromolecular machines, with a structure that is largely conserved from protists to mammals1. Microtubule doublets are structural components of axonemes that contain a number of proteins besides tubulin, and are usually found in arrays of nine doublets arranged around two singlet microtubules. Coordinated sliding of adjacent doublets, which involves a host of other proteins in the axoneme, produces periodic beating movements of the axoneme. We have obtained a three-dimensional density map of intact microtubule doublets using cryo-electron tomography and image averaging. Our map, with a resolution of about 3 nm, provides insights into locations of particular proteins within the doublets and the structural features of the doublets that define their mechanical properties. We identify likely candidates for several of these non-tubulin components of the doublets. This work offers insight on how tubulin protofilaments and accessory proteins attach together to form the doublets and provides a structural basis for understanding doublet function in axonemes.

  1. Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

Correspondence to: Kenneth H. Downing1 Correspondence and requests for materials should be addressed to K.H.D. (Email: khdowning@lbl.gov).


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