The proteasome is a large, polymeric protease complex responsible for the degradation of intracellular proteins and generation of peptides that bind to class I major histocompatibility complex(MHC) molecules. This study identified a new member of proteasomal subunits in turbots(Scophthalmus maximus). The fulllength c DNA sequence of turbot proteasomal subunit was obtained. Sequence analysis indicated that its primary structure is highly similar to that of LMP7 from other vertebrates. The relationship between the turbot LMP7 expression and immune responses to pathogen infection was reported. Quantitative reverse transcriptase polymerase chain reaction showed that LMP7 was expressed differently in various tissues, with higher expression in the spleen, liver, muscle, and skin. The LMP7 expression was the highest at 96 h after challenge with lymphocyctis disease virus(LCDV) and at 12 h after challenge with Vibrio anguillarum in the turbot liver, kidney, and spleen. Furthermore, the LMP7 expression distinctly increased in turbot kidney cells at 24 h after challenge with V. anguillarum and at 96 h after challenge with LCDV. These results indicate that the turbot LMP7 protein participates in immune responses and may play a significant role in the immune process. The proteasome is a large, polymeric protease complex responsible for the degradation of intracellular proteins and generation of peptides that bind to class I major histocompatibility complex (MHC) molecules. This study identified a new member of proteasomal subunits in turbots (Scophthalmus maximus. The sequence analysis indicated that its primary structure is more similar to that of LMP7 from other vertebrates. The relationship between the turbot LMP7 expression and immune responses to pathogen infection was reported. Quantitative reverse transcriptase polymerase chain reaction showed that LMP7 was expressed differently in various tissues, with higher expression in the spleen, liver, muscle, and skin. The LMP7 expression was the highest at 96 h after challenge with lymphocystis disease virus (LCDV) and at 12 h after challenge with Vibrio anguillarum in the turbot liver, kidney, and spleen. Further, the LMP7 ex pression distinctly increased in turbot kidney cells at 24 h after challenge with V. anguillarum and at 96 h after challenge with LCDV. These results indicate that the turbot LMP7 protein participates in immune responses and may play a significant role in the immune process.