Fluorescent Protein-photoprotein Fusions and Their Applications in Calcium Imaging

Photochem Photobiol. 2017 Mar;93(2):448-465. doi: 10.1111/php.12682. Epub 2017 Jan 25.


Calcium-activated photoproteins, such as aequorin, have been used as luminescent Ca2+ indicators since 1967. After the cloning of aequorin in 1985, microinjection was substituted by its heterologous expression, which opened the way for a widespread use. Molecular fusion of green fluorescent protein (GFP) to aequorin recapitulated the nonradiative energy transfer process that occurs in the jellyfish Aequorea victoria, from which these two proteins were obtained, resulting in an increase of light emission and a shift to longer wavelength. The abundance and location of the chimera are seen by fluorescence, whereas its luminescence reports Ca2+ levels. GFP-aequorin is broadly used in an increasing number of studies, from organelles and cells to intact organisms. By fusing other fluorescent proteins to aequorin, the available luminescence color palette has been expanded for multiplexing assays and for in vivo measurements. In this report, we will attempt to review the various photoproteins available, their reported fusions with fluorescent proteins and their biological applications to image Ca2+ dynamics in organelles, cells, tissue explants and in live organisms.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Aequorin / metabolism*
  • Calcium / metabolism*
  • Energy Transfer
  • Luminescent Proteins / chemistry
  • Luminescent Proteins / metabolism*
  • Protein Engineering
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / metabolism*


  • Luminescent Proteins
  • Recombinant Fusion Proteins
  • Aequorin
  • Calcium