Metarodopsin

Metarhodopsin is a protein in the eye's light-sensitive retinal cell (photoreceptor), which can be phosphorylated when illuminated by a special protein (versitax) and conduct an electrochemical signal from the nervous tissue to the light receptors of the retina. It is involved in night and day vision.

Metarhodopsin molecule is a calmodulin binding sensor (CBS), a photoactivated sensor, a monomeric ion channel. The molecule is capable of rapid photoactivation when its internal coordination sphere is saturated with calcium, which causes the channel to change from an open state (transport of Ca2+, SO4-, H+) to a closed state (transport of ions does not occur). Thanks to this system, contractions open only after light has been detected by a photoreceptor neuron. This discovery suggests that photodetectors using metarhodopsins can work well without light. There was a hypothesis that light sensor cells, with the help of metarhodopsis, signal neighboring cells about a sharp loss of light.