Thought to play a role in photoprotection of the coral's resident symbiont microalgae's photosystems from photoinhibition caused by high light levels found near the surface of coral reefs. In deeper water, the fluorescence may be to convert blue light into longer wavelengths more suitable for use in photosynthesis by the microalgal symbionts. Exhibits a smaller absorbance peak at 494 nm. The broad fluorescence emission spectrum peaks at 583 nm. 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), oxidation of Tyr-(N+1) to didehydrotyrosine, and formation of a double bond to the alpha-amino nitrogen of residue Xaa-N. Maturation of the chromophore requires nothing other than molecular oxygen. 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. Belongs to the GFP family.