Fluorescent Proteins:
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Introduction - Aequorin - Green Fluorescent Proteins

Fluorescent Proteins - Green Fluorescent Protein

Green fluorescent protein, GFP, adopts a beta-barrel structure with an alpha-helix inside. This structure is very rigid and the chromophore is in the centre, protected by the protein.

Specific mutations in GFP residues can modulate its fluorescent properties: different blue, cyan, green and yellow variants, have been described. Using these proteins as starting point, different calcium indicators have been developed by fusion of one or two GFP derivatives, a calcium binding protein, such as calmodulin, CaM, and/or a CaM binding peptide.

In general, those indicators can be classified depending on the process that causes calcium signal.

Cameleons are based on a fluorescent resonance energy transfer (FRET) process between two variants of GFP. Camgaroos and pericams can be classified as environment sensitive GFPs and there are also fusion proteins (fusion aequorin-GFP and aequorin-RFP, red fluorescent protein) that present chemiluminescence resonance energy transfer (CRET or BRET) on binding calcium to aequorin.

Green Fluorescent Protein (GFP) From Aequorea Victoria, Gln 80 Replaced With Arg (Protein data bank 1EMB)

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