The G protein alpha s subunit incorporates [3H]palmitic acid and mutation of cysteine-3 prevents this modification

Biochemistry. 1993 Aug 17;32(32):8057-61. doi: 10.1021/bi00083a001.


We investigated whether alpha s could be acylated by palmitate by transfecting COS cells with the cDNA for the wild-type, long form of alpha s and metabolically labeling with [3H]palmitate or [35S]methionine. Cells were separated into particulate and soluble fractions and immunoprecipitated with a specific peptide antibody. [3H]Palmitate was incorporated into both endogenous and transfected alpha s. Inhibition of protein synthesis with cycloheximide did not block the radiolabeling of alpha s with [3H]palmitate. Hydroxylamine treatment caused a release of the tritium radiolabel, demonstrating that the incorporation was through a thioester bond. The tritium radiolabel was base-labile and comigrated with [3H]palmitate on thin-layer chromatography. The third residue of the wild-type alpha s was mutated from a cysteine to an alanine by site-directed mutagenesis. This mutant was expressed in COS cells and localized to the particulate fraction as determined by immunoprecipitation of the [35S]methionine-labeled cells. The cysteine-3 mutant did not undergo radiolabeling with [3H]palmitate, indicating that this residue is crucial for the modification.

MeSH terms

  • Animals
  • Base Sequence
  • Cell Line
  • Cycloheximide / pharmacology
  • Cysteine / genetics*
  • GTP-Binding Proteins / chemistry
  • GTP-Binding Proteins / genetics
  • GTP-Binding Proteins / metabolism*
  • Gene Expression
  • Immunoblotting
  • Immunosorbent Techniques
  • Methionine / metabolism
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed*
  • Palmitic Acid
  • Palmitic Acids / metabolism*
  • Rats
  • Transfection
  • Tritium


  • Palmitic Acids
  • Tritium
  • Palmitic Acid
  • Cycloheximide
  • Methionine
  • GTP-Binding Proteins
  • Cysteine