The G226A mutant of G(sα) highlights the requirements for dissociation of G protein subunits

Ethan Lee, Ronald Taussig, Alfred G. Gilman

Research output: Contribution to journalArticle

110 Scopus citations

Abstract

Adenylylcyclase cannot be activated by hormones or guanine nucleotide analogs in membranes from cells that express the G226A mutant form of G(sα) instead of the wild-type protein. The mutant G(sα) protein appears incapable of undergoing the conformational change necessary for guanine nucleotide-induced dissociation of the G protein α subunit from the βγ subunit complex (Miller, R.T., Masters, S.B., Sullivan, K.A., Beiderman, B., and Bourne, H.R. (1988) Nature 334, 712-715). G226A G(sα) was synthesized in Escherichia coli, purified, and characterized. Examination of the kinetics of dissociation of guanosine 5'-3-O-(thio)triphosphate (GTPγS) suggests that G226A G(sα) is incapable of assuming the conformation necessary for high affinity binding of Mg2+ to the α subunit-GTPγS complex. Associated changes include the failure of Mg2+ and GTPγS to confer resistance to tryptic proteolysis upon the protein, to enhance intrinsic tryptophan fluorescence, or to cause dissociation of α from βγ. However, the GTPase activity of the mutant protein is near normal (at high Mg2+ concentrations), and the protein is capable of activating adenylylcyclase. A similar defect is present in G49V G(sα). Failure of G protein subunit dissociation appears to be the explanation for the phenotypic properties of cells that express G226A G(sα), and this mutation thus highlights the crucial nature of this reaction as a component of G protein action.

Original languageEnglish (US)
Pages (from-to)1212-1218
Number of pages7
JournalJournal of Biological Chemistry
Volume267
Issue number2
StatePublished - Jan 1 1992

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Fingerprint Dive into the research topics of 'The G226A mutant of G(sα) highlights the requirements for dissociation of G protein subunits'. Together they form a unique fingerprint.

  • Cite this