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Green fluorescent protein (GFP) is a small protein that emits bright green fluorescence in blue light. It was first isolated from the jellyfish.

The gene coding for GFP can be expressed in bacteria, and so it is often used as a marker to show successful uptake of a gene by the bacterium.

What is the advantage of using the gene for GFP to produce easily detectable fluorescence, rather than using a gene for an enzyme that produces a fluorescent substance?

Ps. The original question I got was to explain about the disadvantage, which is that GFP may not fluoresce very brightly and so may be difficult to detect.

Thank you for your help.

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    $\begingroup$ Lemme ask you same thing, in reverse: what is the advantage of using a gene for an enzyme that produces a fluorescent substrate, rather than using the gene for GFP to produce easily detectable fluorescence? If you're getting something done directly, why do the same thing indirectly? $\endgroup$ – another 'Homo sapien' May 8 '17 at 9:49
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    $\begingroup$ Possibly because some people discovered how to induce GFP before anyone discovered an enzyme route? If indeed anyone has done that. $\endgroup$ – jamesqf May 8 '17 at 19:28
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    $\begingroup$ If you used a substrate you would have to get it into the sample. This would add variability in terms of penetration, reaction time and diffusion of the reaction product away from the site of interest. Why bother? Just image the GFP directly with none of this hassle. $\endgroup$ – Tom May 9 '17 at 12:44
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GFP has a lot of advantages:

  • The detection of the fluorescence works directly and doesn't need a lysis step or the uptake of a reagent.
  • Fluorescence can be detected directly using a fluorescence or confokal microscope with the cells. This can be done while growing them on plates (works for bacteria and eukaryotic cell culture).
  • You can sort labelled cells using a flow cytometer.
  • direct tagging of proteins and their subsequent localisation on the cell is possible.
  • GFP is rather stable in the cells and not toxic.
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    $\begingroup$ To add to this: GFP will not diffuse out of the cells (or even out of a vesicle) and you can engineer cells to encode your protein of interest with GFP attached. You can even add all sorts of localization tags to GFP and observe where the tag leads your GFP. $\endgroup$ – VonBeche May 8 '17 at 14:36
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There are no genes that I know of that encode proteins, more specifically enzymes, that will catalysed the production of a fluorescent compound from intermediates present in the average cell. Presumably one would need a whole pathway.

So I suspect that the question has never really arisen.

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IIRC, pseudomonas fluorescens produces a carbon-scaffold molecule around iron ions which produces a fluorescent small molecule. But that would probably require expressing multiple enzymes

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