A cysteine residue in helixII of the bHLH domain is essential for homodimerization of the yeast transcription factor Pho4p.
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.
Shao
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Department of Microbiology and Immunology, Allegheny University of the Health Sciences, 2900 Queen Lane, Philadelphia, PA 19102, USA.
Creasy
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Bergman
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D000595:Amino Acid Sequence; D003545:Cysteine / Q000737:chemistry*; D004268:DNA-Binding Proteins; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics; D018257:Helix-Loop-Helix Motifs; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D016271:Proto-Oncogene Proteins c-myc / Q000737:chemistry / Q000235:genetics; D011993:Recombinant Fusion Proteins; D012441:Saccharomyces cerevisiae / Q000737:chemistry*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics
D004268:DNA-Binding Proteins; D004220:Disulfides; D005656:Fungal Proteins; C060292:PHO4 protein, S cerevisiae; D016271:Proto-Oncogene Proteins c-myc; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D003545:Cysteine