A natively unfolded toxin domain uses its receptor as a folding template

J Biol Chem. 2004 May 21;279(21):22002-9. doi: 10.1074/jbc.M313603200. Epub 2004 Mar 5.

Abstract

Natively unfolded proteins range from molten globules to disordered coils. They are abundant in eukaryotic genomes and commonly involved in molecular interactions. The essential N-terminal translocation domains of colicin toxins from Escherichia coli are disordered bacterial proteins that bind at least one protein of the Tol or Ton family. The colicin N translocation domain (ColN-(1-90)), which binds to the C-terminal domain of TolA (TolA-(296-421)), shows a disordered far-UV CD spectrum, no near-UV CD signal, and non-cooperative thermal unfolding. As expected, TolA-(296-421) displays both secondary structure in far-UV CD and tertiary structure in near-UV CD. Furthermore it shows a cooperative unfolding transition at 65 degrees C. CD spectra of the 1:1 complex show both increased secondary structure and colicin N-specific near-UV CD signals. A new cooperative thermal transition at 35 degrees C is followed by the unchanged unfolding behavior of TolA-(296-421). Fluorescence and surface plasmon resonance confirm that the new unfolding transition accompanies dissociation of ColN-(1-90). Hence upon binding the disordered structure of ColN-(1-90) converts to a cooperatively folded domain without altering the TolA-(296-421) structure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatography, Gel
  • Circular Dichroism
  • Colicins / chemistry*
  • Escherichia coli / metabolism
  • Kinetics
  • Microscopy, Fluorescence
  • Protein Binding
  • Protein Denaturation
  • Protein Folding*
  • Protein Structure, Secondary
  • Protein Structure, Tertiary*
  • Surface Plasmon Resonance
  • Temperature
  • Ultraviolet Rays

Substances

  • Colicins