Mitochondria and calcium homeostasis: a tale of three luminescent proteins

In recent years the jellyfish Aequorea victoria has provided the scientific community with a pair of tools of exceptional usefulness: aequorin and the green fluorescent protein (GFP). Whereas the former has played a major rol e in the study of calcium signalling, the latter has sparked the imaginatio n of researchers into a myriad of elegant experiments. The firefly Photinus pyralis has also been of great use, providing a third luminescent protein, luciferase, which is mostly known for its role as a reporter protein. Conc urrent use of these three proteins provides a powerful means of elucidating biological processes with fine spatio-temporal detail. Here we will illust rate how specific molecular engineering of these three proteins provided a set of biological tools capable of generating important data in the held of calcium homeostasis. First, we will show how the use of specifically targe ted aequorin chimeras enabled the measurement of regional Ca2+ concentratio ns; second, how the use of GFP (and derived chromatic mutants) permitted de tailed morphological analyses in living cells; third, how luciferase was us ed to analyse energetic requirements at the subcellular level. Together, th ese three experimental approaches have provided important details on how mi tochondria participate actively in calcium homeostasis. A final note regard ing clinical implications demonstrates the practical usefulness of the data obtained. Copyright (C) 2001 John Wiley & Sons, Ltd.