Structural information involved in the interpretation of the stepwise protein folding process

Calculating the quantity of information present in each step of the protein folding process suggests that the multistep approach requires less information than the one-step model. Quantitative analysis reveals that the amino acids present in the polypeptide chain do not carry enough information to accurately predict the values of the angles Φ and Ψ in folded proteins. This conclusion results from comparing the amount of information carried by amino acids with the quantity of information necessary to determine Φ and Ψ, taking the complete Ramachandran map as the conformational space. It is shown that the two-step model (comprising two stages, the ES and LS) requires less information, owing to the fact that the final predictions of the angles Φ and Ψ can be based on a preexisting ES structure. Analysis based on information theory points to particular zones of the Ramachandran map that appear to play an important role in the context of protein structure prediction.