Engineered luciferase reporter from a deep sea shrimp utilizing a novel imidazopyrazinone substrate
Key findings
Directed evolution of the 19 kDa Oplophorus luciferase subunit through rational design and three phases of random mutagenesis generated NanoLuc with 16 amino acid substitutions. Starting with N166R stabilizing mutation, the first phase yielded C1A4E with 29,000-fold improvement in HEK293 cells. Final optimization with furimazine substrate achieved 2.5 million-fold luminescence enhancement over wild-type in mammalian cells with 150-fold higher specific activity than firefly or Renilla luciferases.
Synthesis and screening of 24 novel coelenterazine analogues identified furimazine as optimal substrate for engineered luciferase variants. Furimazine produced 25-fold brighter luminescence than native coelenterazine with C1A4E variant and 30-fold improvement with NanoLuc. The substrate exhibited greater chemical stability in culture media and lower autoluminescence background than coelenterazine or coelenterazine h, with apparent Km of approximately 10 μM and glow-type signal half-life exceeding 2 hours at room temperature.
NanoLuc functioned as transcriptional reporter with 80-fold higher signal than firefly luciferase, with PEST-appended variant showing 20-minute intracellular half-life enabling rapid response dynamics. Secreted NanoLuc retained activity in culture medium for 15+ hours at 37°C with 99% medium localization. Fusion to p53 detected DNA damage-induced stabilization with 15-fold response, while fusions to GR and PKCα enabled bioluminescence imaging of protein translocation with 1-5 second exposure times versus 3-10 minutes for beetle luciferases.