Differences in stability of recombinant apoaequorin within subcellular compartments

Recombinant acquorin is widely used as an intracellular Ca2+ indicator within live cells. Our data shows that recombinant apoaequorin was unstable within the cytosol, with a half life of approximately 20 minutes. Targeting of the protein to subcellular organelles resulted in an increase in stability which mag be due to either stabilisation of the photoprotein structure or the absence of-the relevant proteases within the organelles. When the apoprotein was reconstituted with the prosthetic group coelenterazine, there was a substantial increase in it's half life in the cytosol. We propose that this variable stability makes aequorin an ideal reporter of gene expression. (C) 1995 Academic Press, Inc.