Structural and thermodynamic characterization of the DNA binding properties of a triple alanine mutant of MATα2

Ailong Ke, Jonathan R. Mathias, Andrew K. Vershon, Cynthia Wolberger

Research output: Contribution to journalArticle


Triply mutated MATα2 protein, α2-3A, in which all three major groove-contacting residues are mutated to alanine, is defective in binding DNA alone or in complex with Mcm1 yet binds with MATa1 with near wild-type affinity and specificity. To gain insight into this unexpected behavior, we determined the crystal structure of the a1/α2-3A/DNA complex. The structure shows that the triple mutation causes a collapse of the α2-3A/DNA interface that results in a reorganized set of α2-3A/DNA contacts, thereby enabling the mutant protein to recognize the wild-type DNA sequence. Isothermal titration calorimetry measurements reveal that a much more favorable entropic component stabilizes the a1/α2-3A/DNA complex than the α2-3A/DNA complex. The combined structural and thermodynamic studies provide an explanation of how partner proteins influence the sequence specificity of a DNA binding protein.

Original languageEnglish (US)
Pages (from-to)961-971
Number of pages11
Issue number7
StatePublished - Jan 1 2002



  • Crystal structure
  • Homeodomain
  • Isothermal titration calorimetry
  • MATα2
  • Protein-DNA interactions
  • Transcription

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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