Clytin is a member of the aequorin family of photoproteins. It is made up of 189 amino acid residues, contains 3 Ca2+-binding sites, and shows 62% homology in amino acid residues to those in aequorin. The cysteine, tryptophan, and histidine residues, and the C-terminal proline, that are conserved in aequorin and clytin may be involved in the Ca2+-activated bioluminescence of the two proteins. Clytin may also prove useful in the determination of Ca2+.
