The gene for the beta-subunit of retinal transducin (Gnb-1) maps to distal mouse chromosome 4, and related sequences map to mouse chromosomes 5 and 8.

The heterotrimeric G protein transducin releases cGMP-phosphodiesterase from inhibition in retinal rod photoreceptor cells when stimulated by light-activated rhodopsin. As a result the level of cGMP goes down, the rod plasma membrane hyperpolarizes, and the release of neurotransmitter is modified. We have used a bovine cDNA for the beta-subunit of transducin (G beta 1) to map its gene Gnb-1 to distal mouse chromosome 4. This cDNA also identified two other homologous sequences in the mouse genome. One of the sequences was on chromosome 5 which we identified as the locus of Gnb-2, a second G protein beta-subunit gene. The other sequence was on chromosome 8 and is either a pseudogene or an as yet undiscovered third G beta-subunit gene, here termed Gnb-3.