title: Entamoeba histolytica: intracellular distribution of the proteasome.
abstract: We have studied the intracellular distribution of proteasome subunits, corresponding to the catalytic (20S) core and the regulatory (19S) cap, in the extracellular protozoan parasite Entamoeba histolytica. Contrary to all cell types described to date, notably mammalian and yeast, in which the proteasome is found in the nucleus and actively imported into it, microscopic analysis and subcellular fractionation of E. histolytica trophozoites show that the proteasome is absent from the nucleus of these cells. We speculate that, given the relative abundance of mono- and multinucleated trophozoites in culture, a relationship may exist between this unusual distribution of the proteasome and the frequent lack of synchrony between karyo- and cytokinesis in this primitive eukaryote.
authors.affiliation: Instituto de Biotechnología, Universidad Nacional Autónoma de México, Avenida Universidad 2001, Cuernavaca, Morelos 62210, Mexico.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Sánchez
authors.forename: Alejandro
authors.initials: A
authors.lastname: Alagón
authors.forename: Roberto P
authors.initials: RP
authors.lastname: Stock
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology; D003546:Cysteine Endopeptidases / Q000032:analysis*; D004748:Entamoeba histolytica / Q000201:enzymology* / Q000648:ultrastructure; D015151:Immunoblotting; D009097:Multienzyme Complexes / Q000032:analysis*; D046988:Proteasome Endopeptidase Complex
chemical_list: D009097:Multienzyme Complexes; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex