7tnt
The tubulin-based conoid from detergent-extract Toxoplasma gondii cells
Structural highlights
FunctionA0A125YWG5_TOXGM Tubulin is the major constituent of microtubules, a cylinder consisting of laterally associated linear protofilaments composed of alpha- and beta-tubulin heterodimers. Microtubules grow by the addition of GTP-tubulin dimers to the microtubule end, where a stabilizing cap forms. Below the cap, tubulin dimers are in GDP-bound state, owing to GTPase activity of alpha-tubulin.[RuleBase:RU000352] Publication Abstract from PubMedTubulin 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. Cryo-ET of Toxoplasma parasites gives subnanometer insight into tubulin-based structures.,Sun SY, Segev-Zarko LA, Chen M, Pintilie GD, Schmid MF, Ludtke SJ, Boothroyd JC, Chiu W Proc Natl Acad Sci U S A. 2022 Feb 8;119(6):e2111661119. doi: , 10.1073/pnas.2111661119. PMID:35121661[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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