How does ubiquitin, a regulatory protein that labels other proteins for destruction, bind to so many different structures? By shuffling between arrangements until it finds the best option, according to Bert de Groot of the Max Planck Institute for Biophysical Chemistry in Göttingen, Germany, and his team.
Forty six of the arrangements were already known from X-ray crystallography of ubiquitin recognition complexes. The researchers followed ubiquitin's structure (pictured) over pico- to microseconds in various solutions and from many angles, showing that all these conformations are likely to be adopted in living cells.
This work adds to evidence that many confirmations of the same protein often exist in dynamic equilibrium before a binding partner comes along, a model that is at odds with the 'induced fit' hypothesis.