title: New comprehension of the apicoplast of Sarcocystis by transmission electron tomography.
abstract: BACKGROUND
  Apicomplexan parasites (like Plasmodium, Toxoplasma, Eimeria and Sarcocystis) contain a distinctive organelle, the apicoplast, acquired by a secondary endosymbiotic process analogous to chloroplasts and mitochondria. The apicoplast is essential for long-term survival of the parasite. This prokaryotic origin implies that molecular and metabolic processes in the apicoplast differ from those of the eukaryotic host cells and therefore offer options for specific chemotherapeutic treatment. We studied the apicoplast in high-pressure frozen and freeze-substituted cysts of Sarcocystis sp. from roe deer (Capreolus capreolus) to get better insight in apicoplast morphology.
  
  
  CONCLUSIONS
  We observed that the apicoplast contains four continuous membranes. The two inner membranes have a circular shape with a constant distance from each other and large-sized protein complexes are located between them. The two outer membranes have irregular shapes. The periplastid membrane also contains large-sized protein complexes, while the outer membrane displays protuberances into the parasite cytoplasm. In addition, it is closely associated with the endoplasmic reticulum by 'contact sites'.
authors.affiliation: Institut für Zoologie/Spezielle Zoologie, Technische Universität Dresden, Helmholtzstrasse 10, D-01062 Dresden, Germany.
authors.forename: Cveta
authors.initials: C
authors.lastname: Tomova
authors.forename: Willie J C
authors.initials: WJ
authors.lastname: Geerts
authors.forename: Thomas
authors.initials: T
authors.lastname: Müller-Reichert
authors.forename: Rolf
authors.initials: R
authors.lastname: Entzeroth
authors.forename: Bruno M
authors.initials: BM
authors.lastname: Humbel
mesh_terms: D000818:Animals; D003670:Deer / Q000469:parasitology; D007425:Intracellular Membranes / Q000378:metabolism / Q000648:ultrastructure*; D046529:Microscopy, Electron, Transmission / Q000379:methods; D046912:Multiprotein Complexes / Q000378:metabolism / Q000648:ultrastructure; D015388:Organelles / Q000378:metabolism / Q000648:ultrastructure*; D015800:Protozoan Proteins / Q000378:metabolism / Q000648:ultrastructure; D012522:Sarcocystis / Q000378:metabolism / Q000648:ultrastructure*; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D046912:Multiprotein Complexes; D015800:Protozoan Proteins