GFP(Green fluorescent protein)

by Kitija Kaulina

GFP (Green fluorescent protein)

• Protein GFP is a protein that fluoresces green. This protein is a name formed from the English names of the first letters (Green Fluorescent Protein).

GFP(Green fluorescent protein)

• Green Fluorescent Protein (GFP) has existed for more than one hundred and sixty million years in one species of jellyfish, Aequorea victoria. The protein is found in the photoorgans of Aequorea. GFP is not responsible for the glow often seen in pictures of jellyfish - that "fluorescence" is actually due to the reflection of the flash used to photograph the jellies.

Aequorea victoria

GFP

• The green fluorescent protein (GFP) is a protein composed of 238 amino acid residues (26.9 kDa) that exhibits bright green fluorescence when exposed to blue light. Although many other marine organisms have similar green fluorescent proteins.

GFP

• The GFP gene can be introduced into organisms and maintained in their genome through breeding, injection with a viral vector, or cell transformation. To date, the GFP gene has been introduced and expressed in many bacteria, yeast and other fungi, fish (such as zebra fish), plant, fly, and mammalian cells, including human.

GFP ribbon diagram

History of GFP

• In 1994 GFP was cloned. Now GFP is found in laboratories all over the world where it is used in every conceivable plant and animal. Flatworms, algae, and pigs have all been made to fluoresce with GFP.

• The importance of GFP was recognized in 2008 when the Nobel Committee awarded Osamu Shimomura, Marty Chalfie and Roger Tsien the Chemistry Nobel Prize "for the discovery and development of the green fluorescent protein, GFP."

Why GFP is so popular?

• GFP as the microscope of the twenty-first century. Using GFP we can see when proteins are made, and where they can go. This is done by joining the GFP gene to the gene of the protein of the interest so that when the protein is made it will have GFP hanging off it. Since GFP fluoresces, one can shine light at the cell and wait for the distinctive green fluorescence associated with GFP to appear.

GFP ready-made

• GFP is a ready-made fluorescent protein, so it is particularly easy to use. Most proteins that deal with light use exotic molecules to capture and release photons. For instance, the opsins in our eyes use retinol to sense light (see the Molecule of the Month on bacteriorhodopsin). These "chromophores" must be built specifically for the task, and carefully incorporated into the proteins.

GFP in microscope

Why GFP?

• Someone might be saying – why?who cares about this little green protein from a jellyfish? But it turns out with amazingly useful in scientific research, because it allows us to look directly into the inner workings of cells. It is easy to find out where GFP is at any given time: you just have to shine ultraviolet light, and any GFP will glow bright green. So here is the trick: you attach the GFP to any object that you are interested in watching. For instance, you can attach it to a virus. Then, as the virus spreads through the host, you can watch the spread by following the green glow. Or, you can attach it to a protein, and watch through the microscope as it moves around inside cells.

GFP structure

GFP structure

• A topology diagram of the folding pattern in GFP. The -sheet strands are shown in light green, a-helices in blue, and connecting loops in yellow. The positions in the sequence that begin and end each major secondary structure element are also given. The anti-parallel strands (except for the interactions between stands 1 and 6) make a tightly formed barrel.

GFP in use

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