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Sequence Analysis of cDNA and Genomic DNA for a Putative Pertussis Toxin-Insensitive Guanine Nucleotide-Binding Regulatory Protein α Subunit
Masaaki Matsuoka, Hiroshi Itoh, Tohru Kozasa and Yoshito Kaziro
Proceedings of the National Academy of Sciences of the United States of America
Vol. 85, No. 15 (Aug. 1, 1988), pp. 5384-5388
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/32156
Page Count: 5
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We have isolated cDNA clones from rat C6 glioma cells coding for several guanine nucleotide-binding regulatory protein (G protein) α subunits (Gα). The cDNA clones were then used to isolate human chromosomal genes. Among human genomic clones isolated by cross-hybridization with the rat cDNA for the α subunit of the inhibitory G protein Gi2, termed Gi2α, a clone designated λ HGi62 was found to contain a sequence that is highly homologous but distinct from any of the known Gα sequences, and we have tentatively designated this sequence Gxα. We have searched a rat brain cDNA library with the Gxα sequence and isolated a cDNA clone containing a rat sequence similar to human Gxα. The cDNA contained a single open reading frame of 1065 nucleotides coding for a protein of 355 amino acids with a calculated molecular weight of 40,879. The amino acid sequence of rat Gxα shows 66% and 40% similarity with rat Gi2α and rat Gsα (the α subunit of the stimulatory G protein), respectively. By RNA blot hybridization analysis, mRNA of ≈ 3.2 kilobases was detected mainly in brain. Interestingly, the deduced amino acid sequence of Gxα predicts that the Gxα protein may be refractory to modification by pertussis toxin since the cysteine residue in the fourth position from the C terminus of pertussis toxin-sensitive Gα is replaced by isoleucine.
Proceedings of the National Academy of Sciences of the United States of America © 1988 National Academy of Sciences