Five years after the Nobel Prize was awarded for work on green fluorescent protein (GFP), extracted from the jellyfish Aequorea victoria, a fluorescent protein has for the first time been identified in a vertebrate. Found in the muscles of the Japanese freshwater eel (juveniles shown swimming above), it has been named UnaG, after the Japanese word for eel, unagi. The protein emits green fluorescence when it binds to bilirubin, a product of the breakdown of heme, the iron component of the blood pigment haemoglobin. UnaG could have immediate medical applications: bilirubin levels are a good indicator of liver function, so can help diagnose diseases such as jaundice, and researchers have successfully used UnaG fluorescence to monitor bilirubin in human samples. Moreover, UnaG’s vertebrate origins mean it has many different properties from the other fluorescent proteins currently known, and so should be particularly useful as a tool for future research.
Written by Emmanuelle Briolat
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