Serine 113 is the site of receptor-mediated phosphorylation of the Dictyostelium G protein α-subunit Gα2

Mei Yu Chen, Peter N. Devreotes, Robert E. Gundersen

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The G protein α-subunit Gα2 is essential to the developmental program of Dictyostelium. Gα2 is transiently phosphorylated on a serine residue(s) following stimulation with extracellular cAMP (Gundersen, R. E., and Devreotes, P. N. (1990) Science 248, 591-593). To aid in defining the function of α-subunit phosphorylation, we identified the site of Gα2 phosphorylation. Comparison of the isoelectric points (pI) of the phosphorylated and nonphosphorylated forms indicated that a single mole of phosphate is added to Gα2. Cleavage at tryptophan residues and immunoprecipitation with a specific peptide antibody localized the phosphorylated serine in the N-terminal 119 residues. Analysis of a series of Gα1 and Gα2 chimeras further confined the site between amino acids 33 and 215. Site-directed mutagenesis of serines between amino acids 33 and 119 produced two mutants that were not phosphorylated, S45A and S113A. Ser113 was identified as the site by sequential Edman degradation of 32P- radiolabeled Gα2 digested with endoproteinase Glu-C. We have expressed the Gα2 mutants S113A, S113I, S113T, and S113D in a Gα2 null cell line to examine the function of phosphorylation.

Original languageEnglish (US)
Pages (from-to)20925-20930
Number of pages6
JournalJournal of Biological Chemistry
Issue number33
StatePublished - Aug 19 1994


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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