Chromatographic resolution and immunologic identification of the α₄₀ and α₄₁ subunits of guanine nucleotide-binding regulatory proteins from bovine brain

A guanine nucleotide-binding regulatory protein (G protein), with subunits designated as α₄₀βγ, was identified and partially resolved from two other purified G proteins, G₀ (α₃₉βγ) and G(i) (α₄₁βγ), found in bovine brain. The α₄₀ G protein subunit served as a substrate for ADP-ribosylation catalyzed by Bordetella pertussis toxin, as did α₃₉ and α₄₁·α₄₀ was shown to be closely related to, but distinct from, α₄₁ by reaction with various peptide antisera. An antiserum generated against a peptide derived from the sequence of a G(iα) clone isolated from a rat C6 glioma cDNA library (Itoh, H., Kozasa, T., Nagata, S., Nakamura, S., Katada, T., Ui, M., Iwai, S., Ohtsuka, E., Kawasaki, H., Suzuki, K., and Kaziro, Y. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 3776-3780) reacted with α₄₀ to the exclusion of all other α subunits tested. Another antiserum generated against a peptide derived from an analogous region of a different G(iα) clone from a bovine brain cDNA library (Nukuda, T., Tanabe, T., Takahashi, H., Noda, M., Haga, K., Haga, T., Ichiyama, A., Kangawa, K., Hiranaga, M., Matsuo, H., and Numa, S. (1986) FEBS Lett. 197, 305-310) reacted exclusively with α₄₁. Evidence is given for the existence of another form of α₄₁ that did not react with either of these two peptide antisera. The antisera were used to survey various rat tissues for the expression of α₄₀ and α₄₁.