High affinity DNA-binding Myc analogs: recognition by an alpha helix

Cell. 1993 Feb 12;72(3):467-76. doi: 10.1016/0092-8674(93)90122-7.


Myc and other basic-helix-loop-helix-leucine zipper (b-HLH-ZIP) proteins bind the sequence CACGTG. Exhaustive mutagenesis in the basic domain identified four amino acids critical for DNA binding with spacing suggestive of an alpha-helical face. Surprisingly, two highly conserved amino acids were nonessential for DNA binding. Circular dichroism demonstrated a DNA-induced alpha-helical transition. A series of analogs were constructed with multiple simultaneous alanine substitutions at nonessential positions and a critical lysine for arginine substitution. In this way 35-fold higher specific affinity for CACGTG was obtained as compared with the basic domain of c-Myc. These b-HLH-ZIP proteins appear to bind the same palindromic sequence and may compete for common sites in vivo. Additionally, a C-terminal basic region clamp motif was identified that was also identifiable in crystal structures from several different families of DNA-binding factors.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alanine / chemistry
  • Amino Acid Sequence
  • Base Sequence
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
  • Binding Sites
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / metabolism*
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Neoplasm Proteins*
  • Oligodeoxyribonucleotides / chemistry
  • Protein Structure, Secondary
  • Proto-Oncogene Proteins c-myc / chemistry
  • Proto-Oncogene Proteins c-myc / metabolism*
  • Structure-Activity Relationship
  • Transcription Factors / chemistry
  • Transcription Factors / metabolism*


  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
  • DNA-Binding Proteins
  • Neoplasm Proteins
  • Oligodeoxyribonucleotides
  • Proto-Oncogene Proteins c-myc
  • TFEB protein, human
  • Transcription Factors
  • Alanine