– GNGT1 is a subunit of transducin. Heterotrimeric G proteins consist of alpha, beta, and gamma subunits. They are membrane-bound GTPases that are linked to 7-TM receptors. They function as signal transducers for the 7-transmembrane-helix G protein-coupled receptors. They are involved as a modulator or transducer in various transmembrane signaling systems. G proteins are bound to GDP in the ‘off’ state. GNGT1 is the gamma subunit of transducin. Ligand-receptor binding results in detachment of the G protein, switching it to an ‘on’ state and permitting Galpha activation of second messenger signaling cascades. There are several types of Galpha proteins; also, some Gbetagamma subunits have active functions. Gbetagamma coupled to H1 receptors can activate PLA2 and Gbetagamma coupled to M1 receptors can activate KIR channels. The beta and gamma chains are required for the GTPase activity, for replacement of GDP by GTP, and G protein-effector interaction.