Transducin: Difference between revisions

Revision as of 11:55, 9 February 2025

Transducin

Transducin is a G protein found in the retina of the eye. It plays a crucial role in the phototransduction cascade, which is the process by which light is converted into electrical signals in the photoreceptor cells.

Structure

Transducin is a heterotrimeric protein composed of three subunits: alpha (_), beta (_), and gamma (_). The alpha subunit is responsible for binding and hydrolyzing GTP, while the beta and gamma subunits form a stable dimer that anchors the protein to the cell membrane.

Function

Transducin is activated by the rhodopsin receptor, a G protein-coupled receptor (GPCR) that is activated by light. When rhodopsin absorbs a photon, it undergoes a conformational change and activates transducin by facilitating the exchange of GDP for GTP on the alpha subunit. The activated alpha subunit then dissociates from the beta-gamma dimer and interacts with phosphodiesterase, leading to a decrease in cGMP levels and the closure of cGMP-gated ion channels. This results in the hyperpolarization of the photoreceptor cell and the transmission of a signal to the brain.

Role in Vision

Transducin is essential for scotopic vision, which is vision under low-light conditions. It is primarily found in rod cells, which are responsible for detecting light intensity and are highly sensitive to low levels of light. In bright light conditions, transducin is less active, and cone cells take over the role of phototransduction.

Related Proteins

Transducin is part of a larger family of G proteins that are involved in various signaling pathways throughout the body. Other members of this family include Gs, Gi, and Gq proteins, each of which interacts with different receptors and effectors to mediate diverse physiological responses.

Clinical Significance

Mutations in the genes encoding transducin subunits can lead to visual disorders. For example, mutations in the GNAT1 gene, which encodes the alpha subunit of transducin, have been associated with night blindness and other retinal dysfunctions.

Related Pages

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-'''Transducin''' is a protein that is integral to the function of [[photoreceptor cells]] in the [[retina]] of the eye. It is a type of [[G protein]], which are proteins that act as molecular switches inside cells, and is involved in the transmission of signals from light-sensitive molecules to other parts of the cell.
+== Transducin ==
+[[File:Rhodopsin-transducin.png|thumb|right|300px|Illustration of the interaction between rhodopsin and transducin.]]
+'''Transducin''' is a [[G protein]] found in the [[retina]] of the [[eye]]. It plays a crucial role in the [[phototransduction]] cascade, which is the process by which light is converted into electrical signals in the [[photoreceptor cells]].
 == Structure ==
-Transducin is a heterotrimeric G protein, meaning it is composed of three different subunits: alpha (Gα), beta (Gβ), and gamma (Gγ). The Gα subunit is the part of the protein that binds to [[guanosine triphosphate]] (GTP) and [[guanosine diphosphate]] (GDP), molecules that are crucial for the protein's function.
+Transducin is a heterotrimeric protein composed of three subunits: alpha (_), beta (_), and gamma (_). The alpha subunit is responsible for binding and hydrolyzing [[GTP]], while the beta and gamma subunits form a stable dimer that anchors the protein to the cell membrane.
 == Function ==
-In the dark, the Gα subunit of transducin is bound to GDP and the protein is inactive. When light hits the retina, it causes a change in the shape of a molecule called [[rhodopsin]], which is located in the photoreceptor cells. This change in shape allows rhodopsin to bind to the Gα subunit of transducin, causing GDP to be released and GTP to bind in its place. This activates the transducin, which then separates from the rhodopsin and splits into its Gα and Gβγ subunits.
+Transducin is activated by the [[rhodopsin]] receptor, a [[G protein-coupled receptor]] (GPCR) that is activated by light. When rhodopsin absorbs a photon, it undergoes a conformational change and activates transducin by facilitating the exchange of GDP for GTP on the alpha subunit. The activated alpha subunit then dissociates from the beta-gamma dimer and interacts with [[phosphodiesterase]], leading to a decrease in [[cGMP]] levels and the closure of cGMP-gated ion channels. This results in the hyperpolarization of the photoreceptor cell and the transmission of a signal to the brain.
+== Role in Vision ==
+Transducin is essential for [[scotopic vision]], which is vision under low-light conditions. It is primarily found in [[rod cells]], which are responsible for detecting light intensity and are highly sensitive to low levels of light. In bright light conditions, transducin is less active, and [[cone cells]] take over the role of phototransduction.
-The Gα subunit, now activated, binds to another protein called [[phosphodiesterase]], activating it as well. This leads to a decrease in the concentration of a molecule called [[cyclic guanosine monophosphate]] (cGMP) in the cell. As the concentration of cGMP decreases, the ion channels that it was keeping open close, leading to a change in the electrical charge of the cell. This change in charge is what ultimately leads to the transmission of a signal to the brain, allowing us to perceive light.
+== Related Proteins ==
+Transducin is part of a larger family of G proteins that are involved in various signaling pathways throughout the body. Other members of this family include [[Gs]], [[Gi]], and [[Gq]] proteins, each of which interacts with different receptors and effectors to mediate diverse physiological responses.
-== Clinical significance ==
+== Clinical Significance ==
-Mutations in the genes that encode for the subunits of transducin can lead to various forms of [[retinal degeneration]], including [[retinitis pigmentosa]] and [[congenital stationary night blindness]]. These conditions are characterized by a progressive loss of vision due to the death of photoreceptor cells in the retina.
+Mutations in the genes encoding transducin subunits can lead to visual disorders. For example, mutations in the GNAT1 gene, which encodes the alpha subunit of transducin, have been associated with [[night blindness]] and other retinal dysfunctions.
-== See also ==
+== Related Pages ==
-* [[G protein]]
+* [[Phototransduction]]
-* [[Photoreceptor cell]]
 * [[Rhodopsin]]
-* [[Phosphodiesterase]]
+* [[G protein-coupled receptor]]
-* [[Retinitis pigmentosa]]
+* [[Retina]]
-* [[Congenital stationary night blindness]]
-[[Category:G proteins]]
+{{Reflist}}
+[[Category:Signal transduction]]
+[[Category:Proteins]]
 [[Category:Vision]]
-[[Category:Eye proteins]]
-[[Category:Signal transduction]]
-{{stub}}