Two Forms of GO Type G Proteins: Identification and Distribution in Various Rat Tissues and Cloned Cells

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Abstract
A Go type G protein distinct from the major species of Go was recently isolated from bovine brain and designated Go*. The cDNAs encoding two forms of mammalian Goα were also isolated and designated GoAα and GoBα. To recognize two forms of Go type G proteins, we raised antibodies in rabbits against two peptides with sequences found only in the respective proteins of murine GoAα (SNTYE‐DAAAYIQTQF) and GoBα (TEAVAHIQGQYESK). Purified anti‐GoAα antibodies reacted with the major species of Goα purified from bovine and rat brain, whereas anti‐GoBα antibodies reacted only with rat Go*α, but not with the major species of Goα or bovine Go*α. These results indicate that the major species of Goα is encoded by GoAα cDNA and Go*α is encoded by GoBα cDNA. Using these antibodies, the distribution of GoA and GoB was studied in various rat tissues and cloned cells. Both GoA and GoB were present in many tissues, but their distribution in peripheral tissues was distinct. GoAα seemed to associate mainly with neural tissues. On the other hand, relatively high concentrations of GoBα were present in the brain, pituitary gland, adipose tissue, lung, and testis. The concentrations of both GoA and GoB in the brain increased during ontogenic development, but the increase in GoB was observed at a later age. Both GoA and GoB were found in such cloned cells as PC 12, NG108‐15, C6, GA‐1, G8, and 3T3‐L1 cells. Treatment of PC 12 cells with nerve growth factor caused the extension of neuron‐like processes and the increase in the level of GoA, but not in the level of GoB.