G protein subunit alpha transducin 1
The GNAT1 gene provides instructions for making a protein called alpha (α)-transducin. This protein is one part (the alpha subunit) of a protein complex called transducin. There are several versions of transducin made up of different subunits. Each version is found in a particular cell type in the light-sensitive tissue at the back of the eye (the retina), where it plays a role in transmitting visual signals from the eye to the brain.
The transducin complex that contains α-transducin is found only in specialized light receptor cells in the retina called rods. Rods are responsible for vision in low-light conditions. When light enters the eye, a rod cell protein called rhodopsin is turned on (activated), which then activates α-transducin. Once activated, α-transducin breaks away from the transducin complex in order to activate another protein called cGMP-PDE, which triggers a series of chemical reactions that create electrical signals. These signals are transmitted from rod cells to the brain, where they are interpreted as vision.
At least two mutations in the GNAT1 gene have been found to cause autosomal dominant congenital stationary night blindness, which is characterized by the inability to see in low light.
One of these mutations impairs the protein's ability to activate cGMP-PDE; the other mutation results in a protein that is constantly turned on (constitutively activated). Both of these mutations disrupt the pathway that creates visual signals to be sent from rod cells to the brain. A nonfunctional α-transducin protein stops the signaling pathway. When α-transducin is constitutively activated, the signals that the rod cells send to the brain are constantly occurring, even in bright light. Visual information from rod cells is then perceived by the brain as not meaningful, resulting in night blindness.
- guanine nucleotide binding protein (G protein), alpha transducing activity polypeptide 1
- guanine nucleotide-binding protein G(t) subunit alpha-1
- guanine nucleotide-binding protein G(T), alpha-1 subunit
- rod-type transducin alpha subunit
- transducin alpha-1 chain
- transducin, rod-specific