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

Research output: Contribution to journalArticle

28 Scopus citations

Abstract

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
Volume254
Issue number2
DOIs
StatePublished - Jan 1 1988
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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