How Is Rhodopsin Activated?

When rhodopsin is activated by light the protein couples with the G protein transducin which is the first step in the signal cascade. Rhodopsin must undergo several conformational changes before being able to bind transducin. Rhodopsin is initially converted to metarhodopsin II which is the active form of rhodopsin.

What enzyme does rhodopsin activate?

Each photoexcited rhodopsin (R*) molecule catalyzes binding of GTP to many copies of the guanine nucleotide-binding protein transducin, which, in its GTP-binding form, then activates cGMP phosphodiesterase (PDEase).

Is rhodopsin activated by light?

(a) Rhodopsin, the photoreceptor in vertebrates, has two parts: the trans-membrane protein opsin, and retinal. ... When light strikes rhodopsin, the G-protein transducin is activated, which in turn activates phosphodiesterase. Phosphodiesterase converts cGMP to GMP, thereby closing sodium channels.