The spectral tuning in the short wavelength-sensitive type 2 pigments

Using site-directed mutagenesis and multiple regression analysis, we have studied the molecular genetics and evolution of short wavelength-sensitive (SWS2) pigments in vertebrates. These analyses suggest that the SWS2 pigment in the vertebrate ancestor had the wavelength of maximum absorption (lambda(max)) of approximately 440 nm and that various lambda(max)'s of the contemporary SWS2 pigments in vertebrates are caused mainly by additive effects of amino acid replacements at ten sites.