The β subunit of the guanine nucleotide regulatory proteins: Identification of its location on two‐dimesional gels of brain tissue and its regional and subcellular distribution in brain

The β subunit of the guanine nucleotide regulatory proteins (also termed G proteins) has been examined in both rat and human brain, a single protein of molecular weight 36,000 daltons and pI 5.8 reacted the antisera. This protein also comigrated with one of the proteins present in a purified preparation of bovine brain G proteins. Based upon molecular weight, pI, and reactiion with specific antisera, it was concluded that this protein is the β subunit of the G proteins in brain. Using this information, the regional and subcellular distribution of the G protein β subunit was studied in rat brain. Of 25 distinct neuroanatomical areas examined, cortical regions were generally found to contain the largest amount of this protein. The subcellular distribution of the G protein β subunit revealed that large amounts are present in the synaptic membrane, crude synaptic vesicles, and microsomes. These studies serve to identify another protein visible on silver‐stained two‐dimensional electrophortograms of rat and human brain. The regional and subcellular distribution of the G protein β subunit correlate well with the proposed physiological function of this protein.