GTP analogues promote release of the α subunit of the guanine nucleotide binding protein, G(i)2, from membranes of rat glioma C6 BU1 cells

G. Milligan, I. Mullaney, C. G. Unson, L. Marshall, A. M. Spiegel, H. McArdle

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The major pertussis-toxin-sensitive guanine nucleotide-binding protein of rat glioma C6 BU1 cells corresponded immunologically to G(i)2. Antibodies which recognize the α subunit of this protein indicated that it has an apparent molecular mass of 40 kDa and a pI of 5.7. Incubation of membranes of these cells with guanosine 5'-[βγ-imido]triphosphate, or other analogues of GTP, caused release of this polypeptide from the membrane in a time-dependent manner. Analogues of GDP or of ATP did not mimic this effect. The GTP analogues similarly caused release of the α subunit of G(i)2 from membranes of C6 cells in which this G-protein had been inactivated by pretreatment with pertussis toxin. The β subunit was not released from the membrane under any of these conditions, indicating that the release process was a specific response to the dissociation of the G-protein after binding of the GTP analogue. Similar nucleotide profiles for release of the α subunits of forms of G(i) were noted for membranes of both the neuroblastoma x glioma hybrid cell line NG108-15 and of human platelets. These data provide evidence that: (a) pertussis-toxin-sensitive G-proteins, in native membranes, do indeed dissociate into α and βγ subunits upon activation; (2) the α subunit of 'G1-like' proteins need not always remain in intimate association with the plasma membrane; and (3) the α subunit of G(i)2 can still dissociate from the β/γ subunits after pertussis-toxin-catalyzed ADP-ribosylation.

Original languageEnglish (US)
Pages (from-to)391-396
Number of pages6
JournalBiochemical Journal
Issue number2
Publication statusPublished - Jan 1 1988
Externally publishedYes


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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