Recognition of the intrinsically flexible addiction antidote MazE by a dromedary single domain antibody fragment. Structure, thermodynamics of binding, stability, and influence on interactions with DNA

J Biol Chem. 2003 Apr 18;278(16):14101-11. doi: 10.1074/jbc.M209855200. Epub 2003 Jan 17.


The Escherichia coli mazEF operon defines a chromosomal addiction module that programs cell death under various stress conditions. It encodes the toxic and long-lived MazF and the labile antidote MazE. The denaturation of MazE is a two-state reversible dimer-monomer transition. At lower concentrations the denatured state is significantly populated. This leads to a new aspect of the regulation of MazE concentration, which may decide about the life and death of the cell. Interactions of MazE with a dromedary antibody domain, cAbMaz1 (previously used as a crystallization aid), as well as with promoter DNA were studied using microcalorimetric and spectroscopic techniques. Unique features of cAbMaz1 enable a specific enthalpy-driven recognition of MazE and, thus, a significant stabilization of its dimeric native conformation. The MazE dimer and the MazE dimer-cAbMaz1 complex show very similar binding characteristics with promoter DNA, i.e. three binding sites with apparent affinities in micromolar range and highly exothermic binding accompanied by large negative entropy contributions. A working model for the MazE-DNA assembly is proposed on the basis of the structural and binding data. Both binding and stability studies lead to a picture of MazE solution structure that is significantly more unfolded than the structure observed in a crystal of the MazE-cAbMaz1 complex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Biochemistry / methods
  • Calorimetry
  • Calorimetry, Differential Scanning
  • Camelus
  • Circular Dichroism
  • DNA / metabolism
  • DNA-Binding Proteins / chemistry*
  • DNA-Binding Proteins / metabolism
  • Dimerization
  • Entropy
  • Escherichia coli / metabolism
  • Escherichia coli Proteins*
  • Immunoglobulin Fragments / chemistry
  • Models, Molecular
  • Molecular Sequence Data
  • Peptides / chemistry
  • Promoter Regions, Genetic
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Sequence Homology, Amino Acid
  • Temperature
  • Thermodynamics
  • Time Factors


  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • Immunoglobulin Fragments
  • MazE protein, E coli
  • Peptides
  • DNA