title: Volutin granules of Eimeria parasites are acidic compartments and have physiological and structural characteristics similar to acidocalcisomes.
abstract: The structural organization of parasites has been the subject of investigation by many groups and has lead to the identification of structures and metabolic pathways that may represent targets for anti-parasitic drugs. A specific group of organelles named acidocalcisomes has been identified in a number of organisms, including the apicomplexan parasites such as Toxoplasma and Plasmodium, where they have been shown to be involved in cation homeostasis, polyphosphate metabolism, and osmoregulation. Their structural counterparts in the apicomplexan parasite Eimeria have not been fully characterized. In this work, the ultrastructural and chemical properties of acidocalcisomes in Eimeria were characterized. Electron microscopy analysis of Eimeria parasites showed the dense organelles called volutin granules similar to acidocalcisomes. Immunolocalization of the vacuolar proton pyrophosphatase, considered as a marker for acidocalcisomes, showed labeling in vesicles of size and distribution similar to the dense organelles seen by electron microscopy. Spectrophotometric measurements of the kinetics of proton uptake showed a vacuolar proton pyrophosphatase activity. X-ray mapping revealed significant amounts of Na, Mg, P, K, Ca, and Zn in their matrix. The results suggest that volutin granules of Eimeria parasites are acidic, dense organelles, and possess structural and chemical properties analogous to those of other acidocalcisomes, suggesting a similar functional role in these parasites.
authors.affiliation: Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho and Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens, Univesidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho, 373, bloco G subsolo, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ 21941-902, Brazil.
authors.forename: Lia Carolina
authors.initials: LC
authors.lastname: Soares Medeiros
authors.forename: Fabio
authors.initials: F
authors.lastname: Gomes
authors.forename: Luis Renato Maia
authors.initials: LR
authors.lastname: Maciel
authors.forename: Sergio Henrique
authors.initials: SH
authors.lastname: Seabra
authors.forename: Roberto
authors.initials: R
authors.lastname: Docampo
authors.forename: Silvia
authors.initials: S
authors.lastname: Moreno
authors.forename: Helmut
authors.initials: H
authors.lastname: Plattner
authors.forename: Joachim
authors.initials: J
authors.lastname: Hentschel
authors.forename: Urara
authors.initials: U
authors.lastname: Kawazoe
authors.forename: Hector
authors.initials: H
authors.lastname: Barrabin
authors.forename: Wanderley
authors.initials: W
authors.lastname: de Souza
authors.forename: Renato Augusto
authors.initials: RA
authors.lastname: Damatta
authors.forename: Kildare
authors.initials: K
authors.lastname: Miranda
mesh_terms: D000595:Amino Acid Sequence; D004539:Eimeria / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D008969:Molecular Sequence Data; D015388:Organelles / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D015800:Protozoan Proteins