Researchers led by Associate Professor Kota Katayama from Nagoya Institute of Technology have uncovered how subtle amino acid substitutions in primate cone pigments enable precise red-green color discrimination.

By analyzing red and green cone pigments from crab-eating macaques, whose color vision closely resembles humans', the team identified three critical amino acid changes—A180S, F277Y, and A285T—that account for the 30 nm spectral shift between the pigments.

These substitutions alter the electrostatic environment around the retinal chromophore rather than changing its geometry, allowing for distinct light absorption wavelengths.

The study, published in Science, also revealed a unique membrane-facing opening in cone pigments absent in rhodopsin, which may explain their faster regeneration rates.

These findings advance understanding of genetic variations affecting color perception and could inform drug development targeting photoreceptors and G protein-coupled receptors.

The research highlights how minute structural changes in cone pigments enable both accurate color discrimination and rapid visual function in bright light.