Second Rhagophthalmid Luciferase Cloned from Chinese Glow-worm Menghuoius giganteus (Rhagophthalmidae: Elateroidea)

The pH-insensitive beetle luciferases cloned from Rhagophthalmidae, Phengodidae, and Elateridae exhibit great potential application as reporter assays for monitoring gene expression. At present, however, only one luciferase has been reported from the enigmatic and predominantly Asian distributed luminous family Rhagophthalmidae. Here, we cloned the second rhagophthalmid luciferase from the Chinese glow-worm Menghuoius giganteus (Rhagophthalmidae: Elateroidea) by combining reverse transcription polymerase chain reaction (RT-PCR) with rapid amplification of complementary DNA ends (RACE). The luciferase consisted of 546 amino acids and showed high identity to that of Rhagophthalmus ohbai (90.4%). The recombinant M. giganteus luciferase was produced in vitro and exhibited significant bioluminescent activity under neutral conditions (pH 7.8), with low K_M for D-luciferin (2.2 μm) and ATP (53 μm). Activity was highest at 10°C and inactivation occurred at 45°C. This luciferase showed pH-insensitivity and maximum emission spectrum at 560 nm. Phylogenetic analyses based on the deduced amino acids indicated a close relationship between the M. giganteus luciferase and that of R. ohbai. These results increase our understanding of rhagophthalmid luciferases and provide a new resource for the application of luciferases.