title: Cu,Zn superoxide dismutases from Tetrahymena thermophila: molecular evolution and gene expression of the first line of antioxidant defenses.
abstract: In the present study, we describe the molecular and functional characterization of two Cu,Zn superoxide dismutase (SOD) genes, named tt-sod1a and tt-sod1b from Tetrahymena thermophila, a free-living ciliated protozoan widely used as model organism in biological research. The cDNAs and the putative amino acid sequences were compared with Cu,Zn SODs from other Alveolata. The primary sequences of T. thermophila Cu,Zn SODs are unusually long if compared to orthologous proteins, but the catalytically important residues are almost fully conserved. Both phylogenetic and preliminary homology modeling analyses provide some indications about the evolutionary relationships between the Cu,Zn SODs of Tetrahymena and the Alveolata orthologous enzymes. Copper-dependent regulation of Cu,Zn SODs expression was investigated by measuring mRNA accumulation and enzyme activity in response to chronic exposure to non-toxic doses of the metal. Our in silico analyses of the tt-sod1a and tt-sod1b promoter regions revealed putative consensus sequences similar to half Antioxidant Responsive Elements (hARE), suggesting that the transcription of these genes directly depends on ROS formation. These data emphasize the importance of complex metal regulation of tt-sod1a and tt-sod1b activation, as components of an efficient detoxification pathway allowing the survival of T. thermophila in continued, elevated presence of metals in the environment.
authors: Department of Biology, via U. Bassi 58/B, University of Padova, 35100 Padova, Italy; Institute for Evolution and Biodiversity, Westfälische Wilhelms-Universität, Münster, Germany.
authors: Diana
authors: D
authors: Ferro
authors: Department of Aquaculture and Fisheries, Agricultural University of Tirana, Tirana, Albania.
authors: Rigers
authors: R
authors: Bakiu
authors: Department of Biology, via U. Bassi 58/B, University of Padova, 35100 Padova, Italy.
authors: Cristiano
authors: C
authors: De Pittà
authors: Department of Biology, via U. Bassi 58/B, University of Padova, 35100 Padova, Italy.
authors: Francesco
authors: F
authors: Boldrin
authors: Department of Biology, via U. Bassi 58/B, University of Padova, 35100 Padova, Italy.
authors: Franco
authors: F
authors: Cattalini
authors: School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy.
authors: Sandra
authors: S
authors: Pucciarelli
authors: School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy.
authors: Cristina
authors: C
authors: Miceli
authors: Department of Biology, via U. Bassi 58/B, University of Padova, 35100 Padova, Italy. Electronic address: gianfranco.santovito@unipd.it.
authors: Gianfranco
authors: G
authors: Santovito
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D003300:Copper / Q000378:metabolism; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D015971:Gene Expression Regulation, Enzymologic; D008969:Molecular Sequence Data; D010802:Phylogeny; D017382:Reactive Oxygen Species / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D013482:Superoxide Dismutase / Q000235:genetics* / Q000378:metabolism*; D016808:Tetrahymena thermophila / Q000201:enzymology* / Q000235:genetics*
chemical_list: D000975:Antioxidants; D016054:DNA, Protozoan; D017382:Reactive Oxygen Species; D003300:Copper; D013482:Superoxide Dismutase
keywords: Cu,Zn superoxide dismutase; Tetrahymena thermophila; ciliated protozoa; copper.; metal-induced oxidative stress