OPN - Opsin receptors | Elisa - Clia - Antibody - Protein

Background:

 Opsin receptors, also known as visual pigments, represent a fundamental component of the visual system in vertebrates, playing a central role in the transduction of light signals into neural impulses. They are a class of G protein-coupled receptors (GPCRs) found predominantly in the photoreceptor cells of the retina. The discovery and understanding of opsins have significantly advanced our comprehension of vision and the mechanisms underlying light perception. The study of opsins traces back to the early 19th century when researchers began investigating the physiological basis of vision. A significant breakthrough came in the mid-20th century when the pioneering work of George Wald and colleagues elucidated the biochemical processes underlying phototransduction, for which Wald was awarded the Nobel Prize in Physiology or Medicine in 1967.

Structural Basis:

Opsin receptors are characterized by their distinctive seven-transmembrane helical structure, a hallmark of GPCRs. These receptors consist of an extracellular N-terminal domain, seven transmembrane helices connected by intracellular and extracellular loops, and an intracellular C-terminal domain. The chromophore molecule retinaldehyde, derived from vitamin A, is covalently bound to a lysine residue within the opsin protein, forming the functional photopigment.

Functional Significance:

Opsin receptors are integral to the process of phototransduction, wherein light energy is converted into electrical signals that can be interpreted by the brain. Upon absorption of photons, the retinaldehyde moiety undergoes a conformational change, triggering a cascade of biochemical events that culminate in the generation of a neural impulse. This signal is then transmitted via the optic nerve to the visual processing centers of the brain, where it is decoded into a perceptual image.

1. Rod Opsins:

·        Rhodopsin (RHO):

·        Rhodopsin is the prototypical rod opsin found in rod photoreceptor cells.

·        It is highly sensitive to low levels of light and is responsible for scotopic (low-light) vision, aiding in night vision and peripheral vision.

·        Rhodopsin consists of a protein called scotopsin and a light-sensitive chromophore molecule called retinaldehyde.

2. Cone Opsins:

·        Short-Wavelength-Sensitive Opsin (SWS1):

·        SWS1 opsin, also known as blue cone opsin, is sensitive to short-wavelength light (blue).

·        It is primarily expressed in cone photoreceptor cells and contributes to color vision and daylight vision.

·        Middle-Wavelength-Sensitive Opsin (MWS, also known as RH2):

·        MWS opsin, also known as green cone opsin, is sensitive to middle-wavelength light (green).

·        It is expressed in cone photoreceptor cells and contributes to color vision, particularly in the green region of the spectrum.

·        Long-Wavelength-Sensitive Opsin (LWS):

·        LWS opsin, also known as red cone opsin, is sensitive to long-wavelength light (red).

·        It is expressed in cone photoreceptor cells and contributes to color vision, particularly in the red region of the spectrum.

3. Additional Opsins:

·        Melanopsin (OPN4):

·        Melanopsin is a non-image-forming opsin found in intrinsically photosensitive retinal ganglion cells (ipRGCs).

·        It plays a role in regulating various non-visual functions, including the regulation of circadian rhythms, pupillary light reflex, and modulation of sleep-wake cycles.

·        Neuropsin (OPN5):

·        Neuropsin is an opsin expressed in the retina and the brain.

·        Its functions are less well-characterized compared to other opsins, but it may be involved in regulating circadian rhythms and light-induced behaviors.

·        Opsin-3 (Panopsin or Encephalopsin):

·        Opsin-3 is a non-image-forming opsin with broad spectral sensitivity, found in various tissues including the retina, brain, and skin.

·        It responds to light across the visible spectrum and into the near-infrared range.

·        Opsin-3 is involved in regulating circadian rhythms, hormone secretion, skin physiology, and other non-visual light responses.

Summary:

Opsin receptors encompass a variety of visual pigments expressed in photoreceptor cells and play essential roles in vision and non-visual light responses. Rod opsins and cone opsins contribute to visual color perception, while non-image-forming opsins such as melanopsin and opsins like neuropsin and opsin-3 regulate various physiological processes beyond vision.