Molecular biology of visual pigments.

We have witnessed exciting advances in the study of vision over the past several years. In particular, our understanding of the biochemical events responsible for visual transduction has grown enormously. By visual trans­ duction we mean those events within the retinal photoreceptor cell that convert a photon stimulus into a neural signal. At center stage are the visual pigments. These light-absorbing molecules initiate an intracellular enzyme cascade that eventually leads either to decreasing (vertebrates) or increasing (invertebrates) plasma membrane cation conductance. I focus in this review on the structure and function of the visual pigments, with emphasis on vertebrates. I have tried throughout to highlight interesting areas in which our knowledge is still incomplete. Recent reviews of this and related topics include Birge 1981, Hargrave 1982, Chabre 1985, Lamb 1986, and Stryer 1986.