Reactome | Gt-GTP dissociates to GNAT1-GTP and GNB1:GNGT1

Gt-GTP dissociates to GNAT1-GTP and GNB1:GNGT1

Stable Identifier

R-HSA-2485182

Type

Reaction [dissociation]

Species

Homo sapiens

Compartment

photoreceptor disc membrane

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Gt-GTP dissociates to GNAT1-GTP and GNB1:GNGT1

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Binding of transducin (Gt) to activated rhodopsin (MII) promotes the release of GDP from the Gt alpha subunit enabling a GTP (present in a higher concentration than GDP) to take its place. With GTP bound, Gt alpha (GNAT1-GTP) dissociates from the Gt beta:gamma subunits (GNB1:GNGT1) and from MII. MII is then available to bind and activate additional transducins. Transducin activation is the first amplifying step in visual transduction. Many findings came from bovine experiments (Pugh & Lamb 1993, Fung & Stryer 1980, Fung et al. 1981, Hofmann 1985).

Literature References

PubMed ID	Title	Journal	Year
6264430	Flow of information in the light-triggered cyclic nucleotide cascade of vision Fung, BK, Hurley, JB, Stryer, L	Proc. Natl. Acad. Sci. U.S.A.	1981
8382952	Amplification and kinetics of the activation steps in phototransduction Pugh, EN, Lamb, TD	Biochim. Biophys. Acta	1993
3933561	Effect of GTP on the rhodopsin-G-protein complex by transient formation of extra metarhodopsin II Hofmann, KP	Biochim. Biophys. Acta	1985
6930647	Photolyzed rhodopsin catalyzes the exchange of GTP for bound GDP in retinal rod outer segments Kwok-Keung Fung, B, Stryer, L	Proc. Natl. Acad. Sci. U.S.A.	1980