title: What does the microsporidian E. cuniculi tell us about the origin of the eukaryotic cell?
abstract: The relationship among the three cellular domains Archaea, Bacteria, and Eukarya has become a central problem in unraveling the tree of life. This relationship can now be studied as the completely sequenced genomes of representatives of these cellular domains become available. We performed a bioinformatic investigation of the Encephalitozoon cuniculi proteome. E. cuniculi has the smallest sequenced eukaryotic genome, 2.9 megabases coding for 1997 proteins. The proteins of E. cuniculi were compared with a previously characterized set of eukaryotic signature proteins (ESPs). ESPs are found in a eukaryotic cell, whether from an animal, a plant, a fungus, or a protozoan, but are not found in the Archaea and the Bacteria. We demonstrated that 85% of the ESPs have significant sequence similarity to proteins in E. cuniculi. Hence, E. cuniculi, a minimal eukaryotic cell that has removed all inessential proteins, still preserves most of the ESPs that make it a member of the Eukarya. The locations and functions of these ESPs point to the earliest history of eukaryotes.
authors.affiliation: Department of Medicine, Medical College of Ohio, Toledo OH 43614, USA.
authors.forename: Alexei
authors.initials: A
authors.lastname: Fedorov
authors.forename: Hyman
authors.initials: H
authors.lastname: Hartman
mesh_terms: D000818:Animals; D019295:Computational Biology; D030562:Databases, Protein; D009670:Encephalitozoon cuniculi / Q000166:cytology / Q000235:genetics*; D005057:Eukaryotic Cells / Q000166:cytology* / Q000502:physiology*; D019143:Evolution, Molecular; D016829:Giardia lamblia / Q000166:cytology / Q000235:genetics*; D015800:Protozoan Proteins / Q000145:classification / Q000235:genetics*; D016415:Sequence Alignment
chemical_list: D015800:Protozoan Proteins