Identification and analysis of an intracellular Cu/Zn superoxide dismutase from Sepiella maindroni under stress of Vibrio harveyi and Cd2+

• A novel intracellular Cu/ZnSOD (SmSOD) was identified from Sepiella maindroni.
• SmSOD mRNA was obviously up-regulated after infection of Vibrio harveyi.
• Time-dependent mRNA expression profile of SmSOD mRNA was found under stress of Cd2+.
• SmSOD might be an acute-phase protein and a marine metal pollution indicator.

Superoxide dismutases (SODs) are ubiquitous family of metalloenzymes involved in protecting organisms from excess reactive oxygen species damage. In this paper, a novel intracellular Cu/ZnSOD from Sepiella maindroni (designated as SmSOD) was identified and characterized. The full-length cDNA sequence of SmSOD (GenBank accession No. KF908850) was 709 bp containing an open reading frame (ORF) of 459 bp, encoding 153 amino acid residues peptide with predicted pI/MW (6.02/15.75 kDa), a 131 bp-5′- and 116 bp-3′- untranslated region (UTR). BLASTn analysis and phylogenetic relationship strongly suggested that the sequence shared high similarity with known Cu/Zn SODs. Several highly conserved motifs, including two typical Cu/Zn SOD family domains, two conserved Cu-/Zn-binding sites (H-47, H-49, H-64, H-120 for Cu binding, and H-64, H-72, H-81, D-84 for Zn binding) and intracellular disulfide bond (C-58 and C-146), were also identified in SmSOD. Time-dependent mRNA expression of SmSOD in hepatopancreas was recorded by quantitative real-time RT-PCR after Vibrio harveyi injection and Cd2+ exposure. The results indicated that SmSOD was an acute-phase protein involved in the immune responses against pathogens and biological indicator for metal contaminants in aquatic environment.