transducin

transducin /trans·du·cin/ (trans-doo´sin) a G protein of the disk membrane of the retinal rods that interacts with activated rhodopsin and participates in the triggering of a nerve impulse in vision.

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transducin

GDP/GTP-regulated protein, composed of three subunits designated α, β and γ, involved in the visual process. Photoactivated rhodopsin activates transducin to bind GTP, the transducin-GTP complex activates G-phosphodiesterase (G-PDE) by removing the inhibitory γ-subunit of G-PDE. The activated G-phosphodiesterase catalyzes the conversion of cGMP to GMP. Since the major action of cGMP is to open Na+-channels, the decrease in cGMP closes the Na+-channels leading to hyperpolarization of the nerve.