Multivalent recognition of ferritin by full‐length NCOA4 enables robust ferritinophagy

Abstract Ferritinophagy is a central pathway in cellular iron homeostasis, yet the molecular basis by which the selective autophagy receptor NCOA4 recognizes and engages ferritin remains poorly defined, largely due to the long‐standing inability of working with a soluble form of the full‐length human NCOA4 (NCOA4 FL ). Here, we present an integrated biochemical and biophysical analysis of NCOA4 FL and its interaction with human ferritin, complemented by structure‐guided modeling. We show that NCOA4 FL is predominantly intrinsically disordered and exists in a dynamic monomer–dimer equilibrium in solution, yet forms a stable, nanomolar‐affinity complex with ferritin. Using crosslinking mass spectrometry, together with integrative modeling informed by low‐resolution structural context, we demonstrate that NCOA4 FL engages ferritin through a multivalent, distributed interface that is not confined to a short motif, in contrast to prior fragment‐based models. Multiple interaction hotspots are identified on ferritin helices B and D, while NCOA4 FL employs both central and terminal regions to wrap around the ferritin nanocage, enabling avidity‐driven recognition. We further show that NCOA4 FL coordinates a redox‐sensitive [4Fe–4S] cluster, introducing a chemically defined feature that may contribute to its conformational plasticity and regulation. Together, these findings establish NCOA4 FL as a flexible, multivalent ferritin receptor and define the recognition logic by which ferritin assemblies are selectively recognized and targeted for lysosomal degradation during ferritinophagy.