Isolation and characterization of a 17-kDa FKBP-type peptidyl-prolyl cis/trans isomerase from Vibrio anguillarum

• 17-kDa FKBP-type PPIase was isolated from Vibrio anguillarum.
• VaFKBP17 exhibited chaperone-like activity by preventing the thermal aggregation.
• VaFKBP17 had the ability to assist refolding of solubilized inclusion body.
• VaFKBP17 was composed of a single domain as FK506-binding/PPIase domain.

Peptidyl-prolyl cis/trans isomerase (PPIase) catalyzes the isomerization of peptide bonds to achieve conformational changes in native folded proteins. An FKBP-type PPIase with an approximate molecular weight of 17 kDa was isolated from Vibrio anguillarum O1 and named VaFKBP17. To investigate its biochemical properties, the ppi gene from V. anguillarum O1 was isolated and overexpressed in Escherichia coli. A protease-coupled assay for isomerization activity, using Succinyl-Ala-Phe-Pro-Phe-p nitroanilide as substrate, indicated that the activity of VaFKBP17 was highest at low temperature (5 °C) and alkaline conditions (pH 10). The immunosuppressant FK506 inhibited the isomerization activity of VaFKBP17. The chaperone activity of VaFKBP17 was assessed using a citrate synthase thermal aggregation activity assay. To evaluate its ability to catalyze protein refolding, the effect of VaFKBP17 on inclusion bodies was investigated during a dilution process. In this assay, VaFKBP17 was able to assist protein refolding. These results provide evidence that VaFKBP17 possesses chaperone-like activity. The structural homology of VaFKBP17 relative to other known bacterial FKBPs was also examined.