Non-fluorescent pigment protein that is mauve in color. The wild-type form is non-fluorescent. Homotetramer. Contains a chromophore consisting of modified amino acid residues. The chromophore is formed by autocatalytic backbone condensation between Xaa-N and Gly-(N+2), and oxidation of Tyr-(N+1) to didehydrotyrosine. Maturation of the chromophore requires nothing other than molecular oxygen. The precise stereochemistry of the tyrosine has not been determined. Fluorescent proteins have become a useful and ubiquitous tool for making chimeric proteins, where they function as a fluorescent protein tag. Typically they tolerate N- and C-terminal fusion to a broad variety of proteins. They have been expressed in most known cell types and are used as a noninvasive fluorescent marker in living cells and organisms. They enable a wide range of applications where they have functioned as a cell lineage tracer, reporter of gene expression, or as a measure of protein-protein interactions. Fluorescence excitation of the Ser-143 mutant is at 587 nm and emission at 622 nm. Belongs to the GFP family. Gurskaya et al., 2001 describe 2 different proteins coming from C.gigantea (cgCP) and C.passiflora (cpCP). Since both C.passiflora and C.passiflora species are synonym, the 2 proteins are merged and some conflicts are reported.