title: The Anti-Oxidant Defense System of the Marine Polar Ciliate Euplotes nobilii: Characterization of the MsrB Gene Family.
abstract: 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 distinctMsrBgenes, encoding enzymes specific for the reduction of the methionine-sulfoxide R-forms, were identified from a draft of theE. nobiliitranscriptionally active (macronuclear) genome. TheEn-MsrBgenes 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 theEn-MsrBgene activity as playing a central role in the genetic mechanism that enablesE. nobiliiand ciliates in general to live in the polar environment.
authors.affiliation: School of Biosciences and Veterinary Medicine, University of Camerino, Camerino 62032, Italy. francesca.ricci@unicam.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: Ricci
authors.affiliation: Singapore Centre for Environmental Life Sciences Engineering (SCELSE), Nanyang Technological University, 60 Nanyang Drive, SBS-01N-27, Singapore 637551, Singapore. flauro@ntu.edu.sg.
authors.forename: Federico M
authors.initials: FM
authors.lastname: Lauro
authors.affiliation: Division of Earth and Ecosystem Sciences, Desert Research Institute, Reno, NV 89512, USA. Joe.Grzymski@dri.edu.
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Grzymski
authors.affiliation: Division of Earth and Ecosystem Sciences, Desert Research Institute, Reno, NV 89512, USA. Robert.Read@dri.edu.
authors.forename: Robert
authors.initials: R
authors.lastname: Read
authors.affiliation: Department of Aquaculture and Fisheries, Agricultural University of Tirana, Tirana 1019, Albania. rigers.bakiu@ubt.edu.al.
authors.forename: Rigers
authors.initials: R
authors.lastname: Bakiu
authors.affiliation: Department of Biology, University of Padova, via U. Bassi 58/B, Padua 35100, Italy. gianfranco.santovito@unipd.it.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Santovito
authors.affiliation: School of Biosciences and Veterinary Medicine, University of Camerino, Camerino 62032, Italy. piero.luporini@unicam.it.
authors.forename: Pierangelo
authors.initials: P
authors.lastname: Luporini
authors.affiliation: School of Biosciences and Veterinary Medicine, University of Camerino, Camerino 62032, Italy. adriana.vallesi@unicam.it.
authors.forename: Adriana
authors.initials: A
authors.lastname: Vallesi
keywords: Euplotes; MsrB proteins; ciliate nano-chromosomes; methionine sulfoxide reductase; oxidative stress; polar microbiology