ChemiBrite cells express a novel variant of clytin, a calcium-activated photoprotein, to enable sensitive luminescent detection of ligand-induced calcium flux. The ChemiBrite version of clytin contains a mutation that increases its affinity for calcium to a level that permits detection of cytosolic calcium in many cells with greater sensitivity than other photoproteins targeted to the mitochondria. Luminescent calcium assays offer several advantages over fluorescent calcium assays including increased sensitivity and lack of interference from fluorescent compounds. CHO cell lines provide investigators with robust platforms for recombinant expression of GPCRs and Ion Channels. We have established an adapted CHO cell line with proven success in multiple expression systems on high throughput platforms. Cloned CHO Parental ChemiBrite cells are made by stable transfection of CHO cells with ChemiBrite clytin. This photoprotein stability-tested cell line is ideal for recombinant expression in luminescent analysis of agonists, antagonists and modulators at the target protein.