Gfp 1 Essay

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, see picture below right. 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.

In Aequorea victoria a protein called aequorin releases blue light upon binding with calcium. This blue light is then totally absorbed by the GFP, which in turn gives off the green light as in the animation below.

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, E. coli 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 is it so popular? Well, I like to think of 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 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.

Check out some of the visually arresting photographs, shown below, that have been taken of fluorescently labeled proteins. Although the pictures are amazing, what they tell us is even more fantastic. Check out Cool Uses for more info.

On this site we will present you with an introduction to GFP. If you are interested in reading more about GFP, there is always Glowing Genes.

 

 

Abstract

The green fluorescent protein (GFP) is a widely used reporter in gene expression and protein localization studies. GFP is a stable protein; this property allows its accumulation and easy detection in cells. However, this stability also limits its application in studies that require rapid reporter turnover. We created a destabilized GFP for use in such studies by fusing amino acids 422–461 of the degradation domain of mouse ornithine decarboxylase (MODC) to the C-terminal end of an enhanced variant of GFP (EGFP). The fusion protein, unlike EGFP, was unstable in the presence of cycloheximide and had a fluorescence half-life of 2 h. Western blot analysis indicated that the fluorescence decay of EGFP-MODC-(422–461) was correlated with degradation of the fusion protein. We mutated key amino acids in the PEST sequence of EGFP-MODC-(422–461) and identified several mutants with variable half-lives. The suitability of destabilized EGFP as a transcription reporter was tested by linking it to NFκB binding sequences and monitoring tumor necrosis factor α-mediated NFκB activation. We obtained time course induction and dose response kinetics similar to secreted alkaline phosphatase obtained in transfected cells. This result did not occur when unmodified EGFP was used as the reporter. Because of its autofluorescence, destabilized EGFP can be used to directly correlate gene induction with biochemical change, such as NFκB translocation to the nucleus.

Footnotes

  • ↵* The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

  • ↵‡ To whom correspondence should be addressed:CLONTECH Laboratories, Inc., 1020 East Meadow Circle, Palo Alto, CA 94303. Tel.: 650-424-8222 (ext. 1134); Fax: 650-354-0776; E-mail: xqli{at}clontech.com.

  • Abbreviations:
    GFP
    green fluorescent protein
    EGFP
    enhanced green fluorescent protein
    MODC
    mouse ornithine decarboxylase
    dEGFP
    destabilized EGFP (EGFP-MODC-(422–461) fusion)
    Tc
    tetracycline
    SEAP
    secreted alkaline phosphatase
    TNF
    tumor necrosis factor
    CHX
    cycloheximide
    CHO
    Chinese hamster ovary
    PBS
    phosphate-buffered saline.
    • Received August 21, 1998.
    • Revision received September 27, 1998.
    • The American Society for Biochemistry and Molecular Biology, Inc.

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