Publication Date
2-8-2022
Journal
Proceedings of the National Academy of Sciences of the United States of America
DOI
10.1073/pnas.2111661119
PMID
35121661
PMCID
PMC8832990
PubMedCentral® Posted Date
2-4-2022
PubMedCentral® Full Text Version
Post-print
Published Open-Access
yes
Keywords
Animals, Cytoskeleton, Electron Microscope Tomography, Microtubule-Associated Proteins, Microtubules, Organelles, Parasites, Protozoan Proteins, Toxoplasma, Tubulin, cryo-electron tomography, subtomogram averaging, tubulin, cytoskeleton, Toxoplasma gondii
Abstract
Tubulin is a conserved protein that polymerizes into different forms of filamentous structures in Toxoplasma gondii, an obligate intracellular parasite in the phylum Apicomplexa. Two key tubulin-containing cytoskeletal components are subpellicular microtubules (SPMTs) and conoid fibrils (CFs). The SPMTs help maintain shape and gliding motility, while the CFs are implicated in invasion. Here, we use cryogenic electron tomography to determine the molecular structures of the SPMTs and CFs in vitrified intact and detergent-extracted parasites. Subvolume densities from detergent-extracted parasites yielded averaged density maps at subnanometer resolutions, and these were related back to their architecture in situ. An intralumenal spiral lines the interior of the 13-protofilament SPMTs, revealing a preferred orientation of these microtubules relative to the parasite’s long axis. Each CF is composed of nine tubulin protofilaments that display a comma-shaped cross-section, plus additional associated components. Conoid protrusion, a crucial step in invasion, is associated with an altered pitch of each CF. The use of basic building blocks of protofilaments and different accessory proteins in one organism illustrates the versatility of tubulin to form two distinct types of assemblies, SPMTs and CFs.
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Biological Phenomena, Cell Phenomena, and Immunity Commons, Biomedical Informatics Commons, Medical Specialties Commons
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