I spent half an hour trying to figure out how to detect two GFP reporters in the same slice from the first figure in this paper, until I realized that the two GFP molecules are recombinant proteins derived from different species, Aequorea victoria and Renilla reniformis, and therefore recognized by different antibodies. The one from the jellyfish aequorea is the common GFP that we normally use and refer to. And this is the first time I’ve heard a GFP from the sea pansy renilla, so I thought to educate myself a little bit basic molecular biology.
The sea pansy renilla is well-known for the luciferase system it provides, which is similar to the resonance fluorescence we see in the firefly during summer time. The luciferase enzyme does an chemicalluminescent reaction and the product fluoresces. What I didn’t know, and what I learned by doing some wikipedia search, is that, the luciferase system in sea pansy is actually coupled to a GFP molecule, which serves as a fluorescent acceptor and hence gives off the green-yellowish color we see. I couldn’t find a structure of the renilla GFP, but I would assume that the two GFPs have different structure and maybe are a result of convergence.
Since I’ve never heard of this renilla GFP, I wonder how many people are aware of its existence and actually taking any advantage of it. My sense is that it’s rarely thought about. So what could be potential benefits of using two different GFPs?
Given that we now almost have a full spectrum’s worth of fluorescent proteins, adding another GFP seems redundant. Imaging cells in cultures using a combination of BFP, CFP, GFP, mCherry and mKate is so widely used and working great. GFP and TdTomato is widely used for imaging in vivo or by immunohistochemistry. Using another GFP might give you a little edge over TdTomato here because of the dimerization of TdTomato, which makes tracking membrane cytoskeletal proteins difficult. GFP on the other hand is a really good monomer to be fused with other proteins. An alternative is to use mKate, a far-red fluorescent protein. It’s relatively new and seems working fine in in vivo imaging at least in here, even though just as a cell tracer. Fusion protein is a totally different situation, although from what I’ve heard and my own stuff, mKate works pretty good too.
Another way of utilizing this GFP is to engineer new optical tools. Since the renilla GFP is a totally different structure, there might be room for tweaks for something cool.