Editing Rod cell (section)

===Reversion to the resting state===
Rods make use of three inhibitory mechanisms (negative feedback mechanisms) to allow a rapid revert to the resting state after a flash of light.

Firstly, there exists a [[rhodopsin kinase]] (RK) which would phosphorylate the cytosolic tail of the activated rhodopsin on the multiple serines, partially inhibiting the activation of [[transducin]]. Also, an inhibitory protein, [[arrestin]], then binds to the phosphorylated rhodopsins to further inhibit the rhodopsin activity.

While arrestin shuts off rhodopsin, an [[Regulator of G protein signalling|RGS]] protein (functioning as a [[GTPase-activating protein]] (GAP)) drives the transducin (G-protein) into an "off" state by increasing the rate of hydrolysis of the bonded GTP to GDP.

When the cGMP concentration falls, the previously open cGMP sensitive channels close, leading to a reduction in the influx of calcium ions. The associated decrease in the concentration of calcium ions stimulates the calcium ion-sensitive proteins, which then activate the guanylyl cyclase to replenish the cGMP, rapidly restoring it to its original concentration. This opens the cGMP sensitive channels and causes a depolarization of the plasma membrane.<ref name="Alberts">Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, Peter Walter (2008). ''Molecular Biology of The Cell'', 5th ed., pp.919-921. Garland Science.</ref>