The following is a summary of the “Rhodopsin, light-sensor of vision,” published in the March 2023 issue of Progress in retinal and eye research by Hofmann, et al.

Rhodopsin is a G-protein-coupled receptor that consists of a polypeptide chain with a bound chromophore, 11-cis-retinal, and has remarkable physicochemical properties. It is responsible for light sensing in vertebrates’ scotopic (low-light) vision. This photopigment is highly stable in the dark, but upon photon absorption, its chromophore isomerizes with an efficiency of 70%, allowing for efficient activation of its G-protein, transducin. The photochemical and biochemical activities of rhodopsin occur on vastly different time scales: the excited state of retinaldehyde is stored in retinal-protein interactions in 1 ps, but it takes milliseconds for the catalytically active state to form, and many tens of minutes for the resting state to be restored. 

Rhodopsin is a protein found in rods that plays a crucial role in phototransduction, and we’ll review its features and function in this review. They begin with an overview of rhodopsin’s overall structure, history, and activation mechanisms. We then talk about how rhodopsin absorbs light and how sensitive it is to different colors of light, how the electrical responses of photoreceptors are triggered by the activity of individual rhodopsin molecules, and how the visual system recovers after being subjected to severe bleaching. 

Next, they give a comprehensive look at rhodopsin’s molecular structure and function, first in its inactive dark state and then in its active Meta states, which regulate its interactions with transducin, rhodopsin kinase, and arrestin. They don’t yet have a full picture of how rhodopsin’s molecular interactions determine the properties of scotopic vision, even though its molecular properties are fine-tuned for phototransduction from starlight to dawn/dusk intensity levels. They outline several significant issues that have yet to be resolved and describe possible future directions for research.

Source: sciencedirect.com/science/article/pii/S1350946222000763