Spectroscopic Analysis of Wavelength Sensitivities of Opsin-Type Photoreceptor Proteins

Abstract

The opsin family is a group of photoreceptive proteins that bind retinal as their chromophore. A growing number of opsin-encoding genes have been identified in animal genomes. Determining the absorption spectra of the opsin-type photoreceptor proteins enables us to predict their contribution to physiological outputs on the basis of their wavelength sensitivities. Here, we describe detailed methods to spectroscopically determine the absorption spectra of recombinant opsin-type proteins that are prepared from cultured cells heterologously expressing them. Our goal is to provide readers with guidelines on how to prepare the solubilized samples from the cells and how to measure the absorption spectra in different preparations. We would highlight advantages and limitations of these approaches.