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| Title | Cryo-tomography reveals rigid-body motion and organization of apicomplexan invasion machinery. |
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| Journal, issue, pages | Nat Commun, Vol. 14, Issue 1, Page 1775, Year 2023 |
| Publish date | Mar 30, 2023 |
 Authors | Long Gui / William J O'Shaughnessy / Kai Cai / Evan Reetz / Michael L Reese / Daniela Nicastro /  |
| PubMed Abstract | The apical complex is a specialized collection of cytoskeletal and secretory machinery in apicomplexan parasites, which include the pathogens that cause malaria and toxoplasmosis. Its structure and ...The apical complex is a specialized collection of cytoskeletal and secretory machinery in apicomplexan parasites, which include the pathogens that cause malaria and toxoplasmosis. Its structure and mechanism of motion are poorly understood. We used cryo-FIB-milling and cryo-electron tomography to visualize the 3D-structure of the apical complex in its protruded and retracted states. Averages of conoid-fibers revealed their polarity and unusual nine-protofilament arrangement with associated proteins connecting and likely stabilizing the fibers. Neither the structure of the conoid-fibers nor the architecture of the spiral-shaped conoid complex change during protrusion or retraction. Thus, the conoid moves as a rigid body, and is not spring-like and compressible, as previously suggested. Instead, the apical-polar-rings (APR), previously considered rigid, dilate during conoid protrusion. We identified actin-like filaments connecting the conoid and APR during protrusion, suggesting a role during conoid movements. Furthermore, our data capture the parasites in the act of secretion during conoid protrusion. |
 External links | Nat Commun / PubMed:36997532 / PubMed Central |
| Methods | EM (subtomogram averaging) |
| Resolution | 28.0 - 49.0 Å |
| Structure data |  EMDB-26873: Subtomogram averages of the 8-nm repeats of the conoid fibers from the cryo-FIB milled Neospora caninum  EMDB-28231: Subtomogram averages of the pre-conoid ring P1 and P2 from the cryo-FIB milled Neospora caninum  EMDB-28234: Subtomogram averages of the pre-conoid ring P3 from the cryo-FIB milled Neospora caninum  EMDB-28246: Composite map of the pre-conoid ring P1, P2 and P3 from the cryo-FIB milled Neospora caninum  EMDB-28247: Subtomogram averages of the 8-nm repeats of the conoid fibers in the protruded states from the cryo-FIB milled Neospora caninum  EMDB-28249: Subtomogram averages of the 8-nm repeats of the conoid fibers in the retracted states from the cryo-FIB milled Neospora caninum |
| Source |
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Neospora caninum (eukaryote)