“I don't think anyone would have thought that eels would have such a bright fluorescent protein,” Robert Campbell, a chemist at the University of Alberta in Edmonton, told Nature. “It's totally different” from other fluorescent proteins, he added. “There's not anything you can point to that's the same.”
One unique feature that distinguishes UnaG from other fluorescent proteins is that it does not produce light with a chromophore within its protein structure. Instead, UnaG fluoresces only when bound with a naturally occurring small molecule found in the eel’s muscles called bilirubin. In humans, bilirubin is produced by the breakdown of haemoglobin. Too much bilirubin in the blood can be toxic. Hospitals test for bilirubin’s levels in the blood to assess liver function and diagnose diseases such as jaundice and anemia. The researchers have used UnaG’s fluorescent properties to design a more sensitive, accurate, and speedier assay for bilirubin levels.
Another unique aspect of UnaG is its capacity to fluoresce in low-oxygen environments, meaning it could be used as a marker for anaerobic regions in cancerous tumors.
“Before the discovery of UnaG, I couldn’t imagine that basic science could have such a direct impact on human health,” Atsushi Miyawaki, a molecular biologist at the RIKEN Brain Science Institute in Japan and senior author on the paper, said in a statement. “From a simple eel, we found a new path to the clinic.”