Does the different domain in sghC1q protein from Cynoglossus semilaevis perform functions independent?

Abstract

In previous research, the full-length sghC1q (CssghC1q) recombinant protein from half-smooth tongue sole (Cynoglossus semilaevis) displayed antibacterial and antiviral activities. However, the roles of the different domains (gC1q and coiled-coil domains) in CssghC1q are still unknown. Thus, in this study, with the help of the pET-28a vector, recombinant proteins comprising different CssghC1q domains were constructed and verified. However, only the recombinant pET-28a-CsgC1q protein was successfully purified. The pET-28a-CsgC1q recombinant protein only exhibited antibacterial activities against Vibrio anguillarum among the bacteria tested. Compared with the full-domain recombinant protein, the recombinant CsgC1q domain exhibited a very low antibacterial activity (10%) at very high protein concentrations (0.1mg/ml). The CsgC1q protein could show 80% antimicrobial activity against V. anguillarum, though a very high concentration (2.25mg/ml) was necessary. The CsgC1q protein, which displayed the antibacterial activities, could require its coiled-coil region to promote correct protein folding; thus, without this domain, the protein would fold inefficiently. The results indicate that the CsgC1q domain may be the key antibacterial activities function domain. However, the CsgC1q domain alone is insufficient for proper antibacterial activity. The coiled-coil region, which is located upstream of the CsgC1q domain, might be important for proper folding and antibacterial activities.