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Understanding the Mechanism of Light Production from Marine Algae
Many different organisms, ranging from bacteria and fungi to fireflies and fish, are endowed with the ability to emit light. This phenomenon, termed bioluminescence, is one of the most fascinating and misunderstood facets of biology. While there are many different bioluminescent organisms, they all have in common a protein known as luciferase. This luciferase takes oxygen from the environment and combines it with a small molecule known as luciferin, literally “light bearer”, resulting in the production of light. The components of these luciferase systems have been known for many years, yet the details of the light production mechanism are poorly understood.
Since arriving at HWI, Dr. Wayne Schultz has been collaborating with Dr. Woodland Hastings of Harvard University to study a unique luciferase system found in marine algae. These single-celled algae respond to disturbances in the water with a brilliant flash of blue light. This phenomenon is known as ocean phosphorescence and exists worldwide. In the past year, Dr. Schultz has succeeded in solving the structure of a light-emitting protein from the algae. This structure is unique among all known luciferase systems and is suggestive of a new mechanism by which light generation can be achieved.
The core structure of the protein is that of a b-barrel, which is represented below by a continuous series of arrows woven together to create a barrel-like structure. In this structure, the barrel is capped at both ends by more protein chains. It is our hypothesis that the barrel must be opened to initiate the light emission, which is believed to originate from the interior of the barrel. Based on the structural studies, it appears that the acidity of the protein solution has an effect on the open or closed state of the barrel. This parallels what is found in nature where the algae can be induced to flash by acidification of their environment. Further studies are being conducted to determine the exact nature of the structural changes in the protein
The detection of light emission, even very small amounts, is relatively easy in the laboratory. Therefore, luciferase systems have become a standard component of many biomedical research techniques. Luciferases have been used to detect the presence of metals and DNA expression in cells. Recently, advances in cancer cell imaging and detection of bacterial contamination have utilized technology provided by the study of luciferases.
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