A cysteine residue in helixII of the bHLH domain is essential for homodimerization of the yeast transcription factor Pho4p

Nucleic Acids Res. 1998 Feb 1;26(3):710-4. doi: 10.1093/nar/26.3.710.


The yeast transcription factor Pho4p is required for expression of the phosphate-repressible acid phosphatase encoded by the PHO5 gene. Functional studies have shown that the molecule is composed of an N-terminal acidic activation domain, a central region which is necessary for interaction with a negative regulatory factor (the cyclin Pho80) and a C-terminal basic helix-loop-helix domain, which mediates DNA binding and homodimerization. In this study the homodimerization domain maps specifically to helixII of this region and a cysteine residue within this region is essential for this function. Experiments support the role of an intermolecular disulfide bond in stabilization of homodimerization, which is critical for DNA binding.

MeSH terms

  • Amino Acid Sequence
  • Cysteine / chemistry*
  • DNA-Binding Proteins*
  • Dimerization
  • Disulfides / chemistry
  • Fungal Proteins / chemistry*
  • Fungal Proteins / genetics
  • Helix-Loop-Helix Motifs*
  • Models, Molecular
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Protein Denaturation
  • Protein Structure, Secondary
  • Proto-Oncogene Proteins c-myc / chemistry
  • Proto-Oncogene Proteins c-myc / genetics
  • Recombinant Fusion Proteins
  • Saccharomyces cerevisiae / chemistry*
  • Saccharomyces cerevisiae Proteins*
  • Sequence Homology, Amino Acid
  • Transcription Factors / chemistry*
  • Transcription Factors / genetics


  • DNA-Binding Proteins
  • Disulfides
  • Fungal Proteins
  • PHO4 protein, S cerevisiae
  • Proto-Oncogene Proteins c-myc
  • Recombinant Fusion Proteins
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • Cysteine