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Transducin is a so-called heterotrimeric G-protein that occurs in the photoreceptor cells of the retina . It is an integral part of the visual signal transduction cascade .

As a G protein, it consists of three different subunits called α, β and γ. The α-subunit binds GDP in the inactive state . The activated rhodopsin now initiates the exchange of GDP for GTP on the α-subunit of the transducin. This breaks down the transducin into the active α-subunit that has bound GTP and the β-γ-subunit. The α-subunit now activates the phosphodiesterase (PDE) by splitting off two inhibitory γ-subunits of the PDE. (For a detailed procedure, see: Visual signal transduction ).

Transducin regenerates itself after some time by the intrinsic GTPase in the α-subunit hydrolyzing the GTP in GDP. The complex with the γ-PDE breaks down and α-transducin now reassembles with the β-γ subunit.

Transducin is also involved in the adaptation to light intensities. Usually this protein is found together with rhodopsin in the outer segment of the photoreceptor cell . However, after prolonged exposure of the retina to light, transducin is shifted to the inner segment of the photoreceptor cell . The transport mechanism is still unclear.

Individual evidence

  1. D. Dell'Orco: A physiological role for the supramolecular organization of rhodopsin and transducin in rod photo receptors. In: FEBS letters. Volume 587, Number 13, June 2013, pp. 2060-2066, ISSN  1873-3468 . doi : 10.1016 / j.febslet.2013.05.017 . PMID 23684654 .
  2. D. Kalra, R. Elsaesser, Y. Gu, K. Venkatachalam: Transducin in rod photoreceptors: translocated when not terminated. In: The Journal of neuroscience: the official journal of the Society for Neuroscience. Volume 27, Number 24, June 2007, pp. 6349-6351, ISSN  1529-2401 . doi : 10.1523 / JNEUROSCI.1399-07.2007 . PMID 17567795 .