MOLECULAR DETERMINANTS OF HUMAN RED GREEN COLOR DISCRIMINATION/

The human red and green color vision pigments are identical at all but 15 of their 364 amino acids, and yet their absorption maxima differ b y 31 nm. In an extensive mutagenesis study, including a set of 28 chim eric proteins modeled after pigments in the color-deficient human popu lation and an additional 30 single and multiple point mutants, the spe ctral difference between these 2 pigments is shown to be determined by 7 and only 7 amino acid residues. In going from the red pigment to th e green pigment, the 7 residues are Ser(116) --> Tyr, Ser(180) --> Ala , Ile(230) --> Thr, Ala(233) --> Ser, Tyr(277) --> Phe, Thr(285) --> A la, and Tyr(309) --> Phe.