Small-world view of the amino acids that play a key role in protein folding

We use geometrical considerations to provide a different perspective on the fact that a few selected amino acids, the so-called key residues, act as nucleation centers for protein folding. By constructing graphs corresponding to protein structures we show that they have the small-world feature of having a limited set of vertices with large connectivity. These vertices correspond to the key residues that play the role of hubs in the network of interactions that stabilize the structure of the transition state.