Guanine nucleotide-binding protein G(T) subunit gamma-T1 is a protein that in humans is encoded by the GNGT1 gene. Either GNGT1 or GNGT2 is the gamma subunit (G<sub>ó</sub>) of the G<sub>òó</sub> part of transducin (written G(T) or G<sub>t</sub>), a heterotrimeric G-protein naturally expressed in vertebrate retina rod and cone cells. GNGT1 only occurs in rod cells, and GNGT2 only occurs in cone cells, with a different alpha (G<sub>ñ</sub>) subunit.