Structural mechanism governing radiationless energy transfer in Renilla bioluminescence

Renilla reniformis, a glowing soft coral, relies on a sophisticated structural mechanism to facilitate radiationless energy transfer during bioluminescence. This process involves the transfer of electronic excitation from one chromophore to another, enabling the conversion of chemical energy into light. Unlike photosynthesis, bioluminescence harnesses the power of enzymatic oxygenation of an energy-rich luciferin to produce light.

The researchers have discovered a 120-kilodalton energy-transfer complex within Renilla reniformis, revealing a heterotetrameric 2:2 assembly. This complex consists of two luciferases loaded with coelenteramide, docked at opposite ends of a dimer of green fluorescent protein (GFP). The distance between the donor and acceptor chromophores is less than 3 nanometers, allowing for efficient Forster-type radiationless energy transfer.

Interestingly, GFP does not merely serve as a color-switchable antenna and luminescence amplifier. It also plays a crucial role in tuning the efficiency of luciferase catalysis by controlling its inherent dynamics. This arrangement enables Renilla bioluminescence to achieve exceptional precision in transferring excited-state energy between chromophores.

The findings provide valuable spatial information about the dipole-dipole coupling within the complex, elucidating the precise organization of donor-acceptor pairs responsible for efficient energy transfer.