Key Amino Acid Residues Responsible for the Color of Green and Yellow Fluorescent Proteins from the Coral Polyp Zoanthus sp.

Site-directed mutagenesis was used to study the structural basis of color diversity of fluorescent proteins by the example of two closely related proteins from one organism (coral polyp Zoanthus sp.), one of which produces green and the other, yellow fluorescence. As a result, the following conversions of emission colors were performed: from yellow to green, from yellow to a dual color (yellow and green), and from green to yellow. The saltatory character of the spectral transitions and the manifestation of the dual-color fluorescence suggest that chemically different fluorophores are responsible for the green and yellow fluorescence. The simultaneous presence of three residues, Gly63, Lys65, and Asp68, is necessary for the efficient formation of the yellow rather than green fluorophore.