title: Cryoelectron tomography reveals periodic material at the inner side of subpellicular microtubules in apicomplexan parasites.
abstract: Microtubules are dynamic cytoskeletal structures important for cell division, polarity, and motility and are therefore major targets for anticancer and antiparasite drugs. In the invasive forms of apicomplexan parasites, which are highly polarized and often motile cells, exceptionally stable subpellicular microtubules determine the shape of the parasite, and serve as tracks for vesicle transport. We used cryoelectron tomography to image cytoplasmic structures in three dimensions within intact, rapidly frozen Plasmodium sporozoites. This approach revealed microtubule walls that are extended at the luminal side by an additional 3 nm compared to microtubules of mammalian cells. Fourier analysis revealed an 8-nm longitudinal periodicity of the luminal constituent, suggesting the presence of a molecule interacting with tubulin dimers. In silico generation and analysis of microtubule models confirmed this unexpected topology. Microtubules from extracted sporozoites and Toxoplasma gondii tachyzoites showed a similar density distribution, suggesting that the putative protein is conserved among Apicomplexa and serves to stabilize microtubules.
authors.affiliation: Department of Molecular Structural Biology, Max Planck Institute for Biochemistry, 82152 Martinsried, Germany. cyrklaff@biochem.mpg.de
authors.forename: Marek
authors.initials: M
authors.lastname: Cyrklaff
authors.forename: Mikhail
authors.initials: M
authors.lastname: Kudryashev
authors.forename: Andrew
authors.initials: A
authors.lastname: Leis
authors.forename: Kevin
authors.initials: K
authors.lastname: Leonard
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Baumeister
authors.forename: Robert
authors.initials: R
authors.lastname: Menard
authors.forename: Markus
authors.initials: M
authors.lastname: Meissner
authors.forename: Friedrich
authors.initials: F
authors.lastname: Frischknecht
mesh_terms: D000818:Animals; D020285:Cryoelectron Microscopy; D005583:Fourier Analysis; D008870:Microtubules / Q000648:ultrastructure*; D008958:Models, Molecular; D010961:Plasmodium / Q000648:ultrastructure*; D034101:Sporozoites / Q000648:ultrastructure*; D014054:Tomography