The N-terminal order-disorder transition is a critical determinant for a metamorphosis of IscU

IscU, a key scaffold protein mediating the biogenesis of iron-sulfur (Fe-S) clusters, exhibits metamorphic characteristics crucial for its versatile and efficient function. Previous studies have demonstrated that IscU has two interconverting conformations: the structured state (S-state) and the disordered state (D-state), each contributing to its distinct functionality and interaction network. Despite its physiological importance, the precise mechanism underpinning the maintenance of IscU’s unique structural heterogeneity has remained elusive. In this study, we used computational and experimental approaches to reveal that the N-terminal order-disorder plays a critical role in the metamorphic modulation of IscU. We found that the N-terminal region displays greater structural plasticity, which is linked to other regions of IscU through coevolutionary relationships. Moreover, we demonstrated that the degree of orderliness in the N-terminal region correlates positively with the stabilization of IscU’s S-state and negatively with its affinity for HscA. This indicates that the flexibility in the N-terminal region is finely tuned to optimize IscU’s physiological efficiency and efficacy. Finally, our data suggest that a peptide mimicking the N-terminal motif can modulate IscU’s metamorphic properties, suggesting a novel therapeutic potential for related pathogenic processes.