A G protein-coupled receptor signaling pathway that starts with an opsin molecule being activated by a photon. Opsins include rhodopsin and others visual receptors bind heterotrimeric transducin G proteins upon activation. Activated transducin alpha-subunit activates cGMP phosphodiesterase, which breaks down cGMP. The decrease in cGMP concentration leads to closure of cGMP-gated (CNG) channels, blockage of Na+ influx, and hyperpolarization of photoreceptor plasma membrane, leading to transmission of signal through synapses. The signal is terminated by phosphorylation of the C-terminal tail of rhodopsin by rhodopsin kinase to allow arrestin to bind and block G protein binding. Typical examples are rhabdomeric photoreceptors in the eyes of deuterostomes.
cGMP-mediated rhodopsin signaling pathway