Chapter 6 Comparative molecular biology of visual pigments

Abstract

This chapter describes the way the existing opsin sequence data have been used to identify important amino acid changes that are responsible for modifying the absorption spectra of visual pigments. Identification of such potentially important amino acid changes is based on the fact that vertebrate ancestors have actually adapted to various photic environments by modifying their visual systems. To understand the molecular genetic basis of spectral tuning of visual pigments, it is essential to establish correlations between a series of the sequences of visual pigments and their λ max values. The potentially important amino acid changes identified in this way have to be tested whether they are in fact responsible for the λ max-shifts using site-directed mutagenesis and cultured cells. The effects of opsin mutants on the folding of visual pigments in cultured cells are reviewed.