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  • So what is GFP?

  • GFP is short for Green Fluorescent Protein

  • and it's a very big deal

  • GFP comes from the jellyfish Aequoria victoria

  • and it's interesting because it's brightly fluorescent green.

  • This means that scientists can stick GFP on the end of another protein

  • and see where that protein goes inside a living cell under the microscope.

  • And because it's quite small at around 27 kDa

  • sticking it on the end of a much larger protein doesn't really affect protein function that much.

  • GFP is built out of a barrel with 11 beta strands

  • and an alpha helix running down the middle.

  • One of the remarkable things about GFP is that it fluoresces on its own

  • without the need for any additional enzymes.

  • This is because of a motif of three important amino acids

  • in the helix running through the centre of that beta barrel.

  • Serine 65, Tyrosine 66 and Glycine 67 are so close together

  • that their chemical groups spontaneously bind together into the GFP chromophore

  • which is fluorescent whenever there's oxygen around.

  • But what if you want to show what happens to a bunch of different proteins at the same time?

  • You'll need more than one colour.

  • And it turns out that mutating key amino acids around this chromophore motif

  • can make subtle changes to the fluorescent colour.

  • This way scientists made yellow and cyan versions of GFP.

  • But what if you need even more colours?

  • Well, scientists discovered another fluorescent protein, called dsRed.

  • This time from the coral Discosoma.

  • The problem with dsRed is that it forms a tetramer

  • so sticking them on a protein would make those proteins bunch together in groups of four.

  • But by making a few key mutations

  • scientists were able to turn dsRed into a monomer called mRFP

  • for Monomeric Red Fluorescent Protein,

  • which was then developed into different colours, such as mOrange, mCherry and mPlum.

  • So by taking two fluorescent proteins from a jellyfish and coral,

  • and a lot of painstaking mutations,

  • scientists have been able to cover the entire colour wheel with fluorescent proteins

  • and by doing so expanded the horizon of biomedical research.

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So what is GFP?

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