Protein binding and folding

BIPH2000 briefly covered the topic of protein folding. If I recalled it right, large proteins required the help of another protein to nudge them into the final native conformation (referred as chaperonins). With this in mind, I searched for an article that talks about these kind of proteins, but it is fascinating that this conformation occurs due to the folding in conformation with the binding of the protein to another protein (in this case an enzyme).

The news and views article entitled "Proteins hunt and gather" reports about proteins, including some involved in critical aspects of biological regulation and signal transduction, are stably folded only in complex with their specific molecular targets. An initial encounter complex, formed through weak interactions, facilitates the formation of a partially structured state, which makes a subset of the final contacts with the target. The conformation allows an efficient search for the final structure adopted by the high-affinity complex. (The figure on the right shows how this conformation occurs).


Taken from the article:

- "Initial, weak, nonspecific interactions, either short or long range, are believed to enhance binding kinetics between well-folded proteins by constraining the diffusional search for a binding site. The results of Sugase et al indicate that this mode of action extends to binding events involving intrinsically disordered proteins. Moreover, coupled folding and binding may further restrict diffusional search within partially structured tethered intermediate states. Notably, this mechanism implies a stepwise reduction in configurational entropy as energetically favourable interactions are formed..."

Thoughts?

Source:
Eliezer, D. and A. G. Palmer (2007). "Biophysics: Proteins hunt and gather." Nature 447(7147): 920-921.