Beschreibung:
<jats:p>Equilibrium denaturation of the 72 amino acid α/β‐protein MerP, by acid, guanidine hydrochloride, or temperature, is fully reversible and follows a two‐state model in which only the native and unfolded states are populated. A <jats:italic>cis</jats:italic>‐<jats:italic>trans</jats:italic> equilibrium around a proline peptide bond causes a heterogeneity of the unfolded state and gives rise to a slow‐ and a fast folding population. With a rate constant of 1.2 s<jats:sup>−1</jats:sup> for the major fast folding population, which has none of the common intrinsically slow steps, MerP is the slowest folding protein of this small size yet reported.</jats:p>