A natively unfolded toxin domain uses its receptor as a folding template.
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.
Anderluh
Gregor
G
School of Cell and Molecular Biosciences, University of Newcastle upon Tyne, Framlington Place, Newcastle upon Tyne, NE2 4HH, United Kingdom.
Gökçe
Isa
I
Lakey
Jeremy H
JH
D002850:Chromatography, Gel; D002942:Circular Dichroism; D003087:Colicins / Q000737:chemistry*; D004926:Escherichia coli / Q000378:metabolism; D007700:Kinetics; D008856:Microscopy, Fluorescence; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020349:Surface Plasmon Resonance; D013696:Temperature; D014466:Ultraviolet Rays
D003087:Colicins