Abstract
The molecular evolution of proteins participating in photo-transduction cascades is analyzed and compared. These proteins generally have high membrane affinities, and it seems likely that they have been evolved to use the membrane surface as an efficient field for signal transduction. The divergence between vertebrate rod and cone subtypes of each protein has a relationship with the others, but diversities are found between vertebrate and invertebrate systems. Existence of protein subtypes and their combinations selectively expressed in a cell type may be one of the molecular bases for the diversity of nervous signal transduction.
