Green Effin' Protein!!

I mentioned last time that green fluorescent protein is one of these sort of serendipitous scientific discoveries that happens every so often, like penicillin.  What, you might ask, is green fluorescent protein?

There have been lots of news stories over the past decade about scientists making various animals glow in the dark.

Glow in the dark bunny!!

Glow in the dark kitties!!!!!!

Glow in the dark adorable baby monkey licking a blanket!!

What these glow in the dark dudes have in common is green fluorescent protein, also affectionately known as GFP.  Each of these organisms has had a bit of DNA encoding the gene for GFP embedded in their cells  so that, in addition to all the other proteins that they normally make, their cells also produce GFP.

But what is GFP and where did it come from?

Green fluorescent protein is, as the name implies, a type of protein that happens to give off fluorescent light when another blue or ultraviolet light source hits it.  Protein may seem like an unlikely candidate to be the agent of biological fluorescence-- after all, who would think that stuff that's in muscle milk and egg whites would be able to glow?  One of the cool things about GFP is that it exemplifies the amazing diversity of tasks that proteins carry out.

As to the where question- the answer is not your local Michael's craft supply shop, though certainly there is no shortage of fluorescent things to be found there.  GFP, despite the rather unearthly glow, is, in fact, a natural product.  It was discovered by a scientist named Osamu Shimomura and it comes from a species of jellyfish that is naturally fluorescent.  That species is called Aequorea victoria.

Aequorea victoria, doing its thing

Osamu Shimomura has been studying Aequorea victoria since the 1960s and shared in a Nobel Prize awarded for the discovery and development of GFP.  Shimomura grew up in 1930s Japan and was a teenager when the atomic bomb fell at Nagasaki; he was 15 miles from ground zero.  The flash blinded him for 30 seconds.

Shimomura went on to study organisms that glow, including Vargula hilgendorfii, whose Japanese name, umi-hotaru, means "sea firefly."  The agent that causes the sea firefly to glow, he found, was a protein he named luciferin.  Luciferin is not fluorescent- it is bioluminescent, which means that it makes light.  Fluorescent proteins don't create their own light- they only appear to "fluoresce" when light of a certain color hits the protein. This work with the sea-fireflies led Shimomura to Princeton to work for a scientist named Frank Johnson.

It was at Princeton that Shimomura began working with jellyfish.  It took 10,000 jellyfish to purify GFP and aequorin, another bioluminescent protein that glows blue.  In jellyfish, the aequorin is the source of bioluminescent light that the GFP uses to give off its own fluorescence, resulting in that cool greenish-bluish glowing color you can see above.  Cool!

And the crazy thing is, Shimomura doesn't really care about all of the applications that GFP has (and it has been adapted for use in thousands of experiments, most of which do not involve cute and cuddly animals).  He just thinks glowing jellyfish are cool and wants to understand how they do their thing.

Here is a fun site devoted to GFP that was a very useful source for this post:  http://www.conncoll.edu/ccacad/zimmer/GFP-ww/