Cameleon was the first genetically encoded calcium sensor that could be used for ratiometric measurements and the first to be used in a transgenic animal to record activity in neurons and muscle cells.
[2] Cameleon and other genetically encoded calcium indicators (GECIs) have found many applications in neuroscience and other fields of biology, including understanding the mechanisms of cell signaling by conducting time-resolved Ca2+ activity measurement experiments with endoplasmic reticulum (ER) enzymes.
[4] The DNA encoding cameleon fusion protein must be either stably or transiently introduced into the cell of interest.
A time-resolved spectroscopy study done on resonance energy transfer by Habuchi et al. in 2002 suggested the existence of 3 different calmodulin conformations that were dependent on Ca2+ binding.
The study concluded that the mechanism of conformation interconversion remains unclear, but the data provided estimates of rate constants, energy transfer efficiency, and donor-acceptor distances in Ca2+-free and Ca2+-bound YC3.1 cameleon proteins.