PMID:12533537

Citation	Lah, J, Marianovsky, I, Glaser, G, Engelberg-Kulka, H, Kinne, J, Wyns, L and Loris, R (2003) 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. 278:14101-11
Abstract	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.
Links	PubMed Online version:10.1074/jbc.M209855200
Keywords	Amino Acid Sequence; Animals; Binding Sites; Biochemistry/methods; Calorimetry; Calorimetry, Differential Scanning; Camels; 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
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