The anti-oxidant defense system of the marine polar ciliate Euplotes nobilii: Characterization of the MsrB gene family

Francesca Ricci, Federico M. Lauro, Joseph J. Grzymski, Robert Read, Rigers Bakiu, Gianfranco Santovito, Pierangelo Luporini, Adriana Vallesi*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)
2 Downloads (Pure)


Organisms living in polar waters must cope with an extremely stressful environment dominated by freezing temperatures, high oxygen concentrations and UV radiation. To shed light on the genetic mechanisms on which the polar marine ciliate, Euplotes nobilii, relies to effectively cope with the oxidative stress, attention was focused on methionine sulfoxide reductases which repair proteins with oxidized methionines. A family of four structurally distinct MsrB genes, encoding enzymes specific for the reduction of the methionine-sulfoxide R-forms, were identified from a draft of the E. nobilii transcriptionally active (macronuclear) genome. The En-MsrB genes are constitutively expressed to synthesize proteins markedly different in amino acid sequence, number of CXXC motifs for zinc-ion binding, and presence/absence of a cysteine residue specific for the mechanism of enzyme regeneration. The En-MsrB proteins take different localizations in the nucleus, mitochondria, cytosol and endoplasmic reticulum, ensuring a pervasive protection of all the major subcellular compartments from the oxidative damage. These observations have suggested to regard the En-MsrB gene activity as playing a central role in the genetic mechanism that enables E. nobilii and ciliates in general to live in the polar environment.

Original languageEnglish
Article number4
Number of pages13
Issue number1
Publication statusPublished - Mar 2017
Externally publishedYes

Bibliographical note

Copyright the Author(s) 2017. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.


  • methionine sulfoxide reductase
  • MsrB proteins
  • oxidative stress
  • polar microbiology
  • ciliate nano-chromosomes
  • Euplotes

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