Transducin
![Sensory rhodopsin II (rainbow colored) embedded in a lipid bilayer (heads red and tails blue) with Transducin below it. Gtα is colored red, Gtβ blue, and Gtγ yellow. There is a bound GDP molecule in the Gtα-subunit and a bound retinal (black) in the rhodopsin. The N-terminus terminus of rhodopsin is red and the C-terminus blue. Anchoring of transducin to the membrane has been drawn in black.](/Images/godic/202502/17/Rhodopsin-transducin0133.png")
Transducin (Gt) is a protein naturally expressed in vertebrate retina rods and cones and it is very important in vertebrate phototransduction. It is a type of heterotrimeric G-protein with different α subunits in rod and cone photoreceptors.
Light leads to conformational changes in rhodopsin, which in turn leads to the activation of transducin. Transducin activates phosphodiesterase, which results in the breakdown of cGMP. The intensity of the flash response is directly proportional to the number of transducin activated.