transducint

Transducin is a guanine nucleotide-binding protein, often referred to as a G protein, that plays a crucial role in visual signal transduction in vertebrates. It is a heterotrimeric G protein, meaning it is composed of three different subunits: alpha (Tα), beta (Tβ), and gamma (Tγ). In the retina, transducin is activated by light. Specifically, the pigment rhodopsin, located in the outer segments of rod photoreceptor cells, absorbs a photon of light. This absorption triggers a conformational change in rhodopsin, which in turn activates transducin. The activated transducin then interacts with phosphodiesterase (PDE), an enzyme that breaks down cyclic guanosine monophosphate (cGMP). The reduction in cGMP levels leads to the closure of ion channels in the photoreceptor cell membrane, ultimately resulting in a hyperpolarization of the cell and the transmission of a visual signal to the brain. Transducin is essential for the amplification of the visual signal, allowing us to perceive even very dim light. Mutations or deficiencies in transducin can lead to visual impairments such as retinitis pigmentosa.