Impact of trifluoroethanol-induced structural changes on luciferase cleavage sites

Induction of structural changes in firefly luciferase were identified by proteolytic digestion, activity measurement and spectroscopic tools upon treatment with 2,2,2-trifluoroethanol (TFE). Our results show that the conformation and function of luciferase change according to TFE concentration. Limited addition of TFE (below 10%) alters the tertiary structure and proteolytic rate with a similar digestion pattern, without noticeable changes in the secondary structure. Conformational changes result in loss of enzymatic activity. More addition of TFE (between 20% and 30%) disrupts the tertiary structure, and consequently the activity completely disappears without recovery upon dilution. Furthermore, at high protein concentration, significant aggregation is observed in this range of TFE concentration. A further increase in TFE concentration (above 30%) induces more helical structure, which is more resistant to tryptic attack. Overall, in spite of large conformational changes of luciferase induced by TFE, the prime-sites of proteolytic cleavage are still located at the same chain segments.