title: Evidence for methionine-sulfoxide-reductase gene transfer from Alphaproteobacteria to the transcriptionally active (macro)nucleus of the ciliate, Euplotes raikovi.
abstract: BACKGROUND
  Deleterious phenomena of protein oxidation affect every aerobic organism and methionine residues are their elective targets. The reduction of methionine sulfoxides back to methionines is catalyzed by methionine-sulfoxide reductases (Msrs), enzymes which are particularly active in microorganisms because of their unique nature of individual cells directly exposed to environmental oxidation.
  
  
  RESULTS
  From the transcriptionally active somatic genome of a common free-living marine protist ciliate, Euplotes raikovi, we cloned multiple gene isoforms encoding Msr of type A (MsrA) committed to repair methionine-S-sulfoxides. One of these isoforms, in addition to including a MsrA-specific nucleotide sequence, included also a sequence specific for a Msr of type B (MsrB) committed to repair methionine-R-sulfoxides. Analyzed for its structural relationships with MsrA and MsrB coding sequences of other organisms, the coding region of this gene (named msrAB) showed much more significant relationships with Msr gene coding sequences of Rhodobacterales and Rhizobiales (Alphaproteobacteria), than of other eukaryotic organisms.
  
  
  CONCLUSIONS
  Based on the fact that the msrAB gene is delimited by Euplotes-specific regulatory 5' and 3' regions and telomeric C4A4/G4T4 repeats, it was concluded that E. raikovi inherited the coding region of this gene through a phenomenon of horizontal gene transfer from species of Alphaproteobacteria with which it coexists in nature and on which it likely feeds.
authors.forename: Nicoleta
authors.initials: N
authors.lastname: Dobri
authors.forename: Annalisa
authors.initials: A
authors.lastname: Candelori
authors.forename: Francesca
authors.initials: F
authors.lastname: Ricci
authors.forename: Pierangelo
authors.initials: P
authors.lastname: Luporini
authors.forename: Adriana
authors.initials: A
authors.lastname: Vallesi
mesh_terms: D020561:Alphaproteobacteria / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics*; D016798:Ciliophora / Q000235:genetics*; D016812:Euplotes / Q000235:genetics*; D008715:Methionine / Q000031:analogs & derivatives / Q000235:genetics; D051150:Methionine Sulfoxide Reductases / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D010084:Oxidation-Reduction; D020033:Protein Isoforms / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D020033:Protein Isoforms; D008715:Methionine; D051150:Methionine Sulfoxide Reductases; C027219:methionine sulfoxide reductase; C013111:methionine sulfoxide