title: A novel polymer of tubulin forms the conoid of Toxoplasma gondii.
abstract: Toxoplasma gondii is an obligatory intracellular parasite, an important human pathogen, and a convenient laboratory model for many other human and veterinary pathogens in the phylum Apicomplexa, such as Plasmodium, Eimeria, and Cryptosporidia. 22 subpellicular microtubules form a scaffold that defines the cell shape of T. gondii. Its cytoskeleton also includes an intricate apical structure consisting of the conoid, two intraconoid microtubules, and two polar rings. The conoid is a 380-nm diameter motile organelle, consisting of fibers wound into a spiral like a compressed spring. FRAP analysis of transgenic T. gondii expressing YFP-alpha-tubulin reveals that the conoid fibers are assembled by rapid incorporation of tubulin subunits during early, but not late, stages of cell division. Electron microscopic analysis shows that in the mature conoid, tubulin is arranged into a novel polymer form that is quite different from typical microtubules.
authors.affiliation: Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA. huke@mail.sas.upenn.edu
authors.forename: Ke
authors.initials: K
authors.lastname: Hu
authors.forename: David S
authors.initials: DS
authors.lastname: Roos
authors.forename: John M
authors.initials: JM
authors.lastname: Murray
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D002453:Cell Cycle / Q000502:physiology; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D008164:Luminescent Proteins / Q000235:genetics; D008854:Microscopy, Electron; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D015388:Organelles / Q000378:metabolism* / Q000648:ultrastructure; D010507:Periodicity; D011108:Polymers / Q000378:metabolism*; D014122:Toxoplasma / Q000378:metabolism* / Q000648:ultrastructure; D014404:Tubulin / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; D008164:Luminescent Proteins; D011108:Polymers; D014404:Tubulin; C054562:yellow fluorescent protein, Bacteria