Department of Biology
130 College Place
Syracuse, New York 13244 USA
presenter: Shozo Yokoyama
In many fish, bird, amphibian, reptilian, and mammalian species, ultraviolet (UV) vision has profound effects on the evolution of organisms by affecting such behaviors as mating preference and foraging strategies. UV vision is determined by visual pigments, each of which consists of the chromophore, 11-cis-retinal, and a transmembrane protein, an opsin. The UV pigments have the maximum wavelengths of absorption (lambda-max) at around 360 nm, whereas evolutionarily closely related violet (or blue) pigments have lmax values at 390- 420 nm.
We have successfully interchanged the color-sensitivities of the mouse ultraviolet pigment (lambda-max = 358 nm) and the human blue pigment (lambda-max = 414 nm) by introducing forward and reverse mutations at five sites. This unveils for the first time the general mechanism of ultraviolet vision. Most contemporary ultraviolet pigments in vertebrates have maintained their ancestral functions by accumulating no more than one of the five specific amino acid changes. The avian lineage is an exception, where the ancestral pigment lost ultraviolet-sensitivity but some descendants regained it by one amino acid replacement at another site.
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