by Andre on 1 February 2006
This is the story of a jellyfish invasion that you may not have heard of. It has nothing to do with broken Japanese fishing nets or painful scuba diving trips. Instead, it’s about how a protein isolated from a luminescent jellyfish in Washington is shedding light on the inner workings of life.
The creature we’re interested in is called Aequorea victoria and is found on the Pacific coast of Washington and British Columbia. According to the Monteray Bay Aquarium, A. victoria is
graceful and nearly transparent, these jellies have long, delicate tentacles. When disturbed, they give off a green-blue glow because of more than 100 tiny, light-producing organs surrounding its outer bell. They can expand their mouths when feeding to swallow jellies half their size.
The jellies’ glow comes from the interaction of two proteins: aequorin and green fluorescent protein (GFP). Aequorin emits blue light when it reacts with calcium and this light then excites GFP which in turn emits in the green portion of the spectrum.
This already appeals to the naturalist in me, but things really picked up on the biophysics side after the gene for GFP was determined by Douglas Prasher then at the Woods Hole Oceanographic Institute.* With the gene in hand, Martin Chalfie, in collaboration with Prasher, was able to use the tools of molecular biology to express the gene in prokaryotes (e. coli) and eukaryotes (c. elegans). To many peoples’ surprise, the cells’ product was fluorescent and that meant that A. victoria was not doing any funky species-specific chemistry to make functional GFP. In the same year, the final critical step to start the GFP revolution rolling was accomplished by Tulle Hazelrigg who attached the gene for GFP to the gene for another protein of interest and showed that the resulting fusion protein would light up, indicating the position of the expressed protein in a cell.
Depending on your background that might not seem like a huge breakthrough, but remember that cells are mostly water so when you look at them in a light microscope you typically don’t see much more than the cell boundary and the nucleus. You can stain cells chemicals of interest and then look at them but this usually kills the cells and so makes studying dynamics within a cell impossible. On the other hand, with GFP fusion proteins and modern microscopes you can watch a living cell expressing proteins in real time at the single molecule level opening up a whole world of dynamics with high precision.
The applications are widespread and significant and I won’t even pretend to survey them. If you want to get an idea of how useful GFP has proven, just try a google scholar search for “green fluorescent protein”. Instead of looking at the details of applications, I would like to remind you that it was an incredible chain of discoveries that lead directly from observing glowing jelly fish to discovering the inner workings of glowing cells by shining blue light on them. You couldn’t have predicted that kind of connection, but there it is, for all to see. In my humble opinion, other ways of knowing about the universe just can’t compete with that. On that note, I would like to leave you to consider the words of the late, great Richard Feynman in an uncharacteristically reverent moment:
Nature uses only the longest threads to weave her patterns, so that each small piece of her fabric reveals the organization of the entire tapestry.
*Prasher didn’t get tenure at Woods Hole despite publishing a paper that now has over 1900 citations (and another with over 600). Ouch.