G protein-coupled photoreceptor activity

Definition

Target type: molecularfunction

Combining with incidental electromagnetic radiation, particularly visible light, and transmitting the signal across the membrane by activating an associated G-protein; promotes the exchange of GDP for GTP on the alpha subunit of a heterotrimeric G-protein complex. [GOC:bf, GOC:dph, ISBN:0198506732]

G protein-coupled photoreceptor activity is a complex process that involves the detection of light by a specialized photoreceptor protein embedded in the cell membrane. These photoreceptor proteins, also known as rhodopsin-like receptors, typically consist of seven transmembrane domains and are coupled to heterotrimeric G proteins. When light strikes the photoreceptor protein, it undergoes a conformational change, triggering a cascade of events that ultimately leads to a cellular response.

Here's a detailed breakdown of the molecular function:

1. **Light Absorption:** The photoreceptor protein contains a chromophore, typically retinal, which absorbs light energy. This absorption causes the chromophore to isomerize from its cis form to its trans form.

2. **Conformational Change:** The isomerization of the chromophore induces a conformational change in the photoreceptor protein, activating its intracellular signaling domain.

3. **G Protein Coupling:** The activated photoreceptor protein interacts with a heterotrimeric G protein, typically a G protein belonging to the Gq family. This interaction causes the G protein to dissociate into its alpha subunit and beta-gamma subunits.

4. **Signal Transduction:** The activated alpha subunit of the G protein, bound to GTP, interacts with downstream effector proteins. These effector proteins can be various enzymes, such as phospholipases or adenylyl cyclases, which trigger second messenger pathways.

5. **Cellular Response:** The activation of effector proteins ultimately leads to a cellular response, such as changes in membrane potential, ion permeability, gene expression, or other cellular functions.

In summary, G protein-coupled photoreceptor activity involves a tightly regulated sequence of events: light absorption, conformational change, G protein activation, signal transduction, and cellular response. This process is essential for vision, as it allows the eye to detect light and transmit signals to the brain for visual perception.'
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Proteins (2)

Compounds (3)