Not only terrestrial but also marine organisms can produce and emit light. Bioluminescence helps them to communicate and attract food, among other things. Martin Marek from the Loschmidt Laboratories at RECETOX, Faculty of Science has been studying this phenomenon in selected marine organisms for several years.
His research has the potential to inspire technological and industrial solutions and the design of environmentally friendly light sources with zero electricity consumption. The practical aspects of the project have been supported in recent years by a proof-of-concept grant from the Masaryk University Technology Transfers Office.
The enzymes responsible for bioluminescence are luciferases, which convert a substrate called luciferin into light in organisms. In recent years, Mark and his colleagues have succeeded in describing the molecular basis of the luciferase reaction in two marine invertebrates, the deep-sea shrimp Oplophoprus gracilirostris and the violet goby Renilla reniformis.
How organisms change the colour of light
“In the new project, we would like to focus on another phenomenon called resonant transmission of bioluminescent energy. This allows some organisms to change the colour of the light they emit in response to their environment. Using luciferase, these organisms chemically transform the substrate to produce a photon of visible light. The energy of this photon is used to excite a fluorescent acceptor protein, which then emits light of a longer wavelength than that received. The organism then glows green, yellow and so on instead of blue,” explains the biochemist.
The scientists want to understand the physical interaction between bioluminescent and fluorescent proteins during energy transfer, including their proximity to each other and their orientation. This is important for understanding the principle of non-radiative energy transfer, where proteins transfer energy through highly efficient dipole-dipole interactions. “The simple idea is that luciferase generates a photon, but in the process the photon is what we call virtual. In actual fact, it disappears before it gains any physical significance because it transfers the energy to another protein, which then emits the light at a different wavelength,” says Marek.
In addition, he and his colleagues have already discovered that it is not just a simple matter of transferring energy and changing the colour of the emitted light. “Initially, scientists thought that fluorescent proteins were just passive energy harvesters but now we know that they actively interact with luciferase and significantly improve its catalytic abilities, which improves the efficiency of the whole bioluminescence process.”
The experts from the Loschmidt Laboratories now plan to analyse the structure of these macromolecular complexes, which combine bioluminescent and fluorescent proteins, and to visualise the entire energy transfer process. The findings will serve as a basis for the design of genetically encodable, colour-tunable and energy-efficient bioluminescent tools for use in biotechnology and biomedicine, for example in the diagnosis of certain diseases.
Producing enzymes
Although Marek studies these processes in marine animals, he does not work with these animas directly. He uses the genes that encode the relevant enzymes in the organisms he studies. These are synthesised in the laboratory and then, using structural biology and biochemical methods, the scientists produce naturally occurring complexes of these enzymes, which are subjected to further analysis. “Once we understand the relationships between the molecules in the complex, we can start to modify and try to improve these systems to look for applications in other areas,” adds the scientist.
He also notes that not all organisms produce complexes of molecules that link bioluminescence to fluorescence. For example, the deep-sea shrimp does not have them and emits only blue
light. However, the researchers in Brno are working with scientists in other countries to overcome this problem and have already identified other organisms in which they can study this phenomenon.