Once metarhodopsin II is formed, it activates transducin by facilitating the exchange of GDP for GTP on the alpha subunit of transducin. This activated transducin then activates phosphodiesterase (PDE), which hydrolyzes cyclic GMP (cGMP). The reduction in cGMP levels causes the closure of cGMP-gated ion channels, leading to hyperpolarization of the rod cell membrane and the generation of an electrical signal.
