Mutant Firefly Luciferase Enzymes Resistant to the Inhibition by Sodium Chloride

ObjectivesFirefly luciferase, one of the most extensively studied enzymes, has numerous applications. However, luciferase activity is inhibited by sodium chloride. This study aims to expand the applications of firefly luciferase in the presence of sodium chloride.ResultsWe first obtained two mutant luciferase enzymes whose inhibition were alleviated and identified these mutations as Val288Ile and Glu488Val. Under dialysis condition (140 mM sodium chloride), the wild type was inhibited to 44% of its original activity level. In contrast, the single mutants, Val288Ile and Glu488Val, retained 67% and 79% of their original activity, respectively. Next, we introduced Val288Ile and Glu488Val mutations into the wild-type luciferase to create a double mutant using site-directed mutagenesis. Notably, the double mutant retained its activity more than 95% of that in the absence of sodium chloride.ConclusionsThe mutant luciferase, named luciferase CR, was found to retain its activity in various concentrations of sodium chloride. The inhibition of luciferase CR under dialysis condition was more alleviated than either Val288Ile or Glu488Val alone, suggesting that the effect of the double mutation was cumulative. We discussed the effect of mutations on the alleviation of the inhibition by sodium chloride.