High-resolution structures of inhibited GAPDH oligomers and full-length human RAD52: From plant metabolism to human homologous recombination

Intrinsically disordered regions and flexible protein segments are key regulatory elements, often becoming ordered only upon interaction with partner domains, ligands, or protein subunits. In this talk, I will present two examples in which disorder is central to protein function: inhibited plant AB-GAPDH oligomers and full-length human RAD52. Using cryo-EM data collected at the EMBL Imaging Centre, together with SEC-SAXS and integrative modeling, we investigated these systems across different degrees of structural order and flexibility. In plant AB-GAPDH, inhibition is driven by redox regulation of the C-terminal extension of the B-subunits and changes in cofactor binding. We resolved multiple inhibited oligomeric forms, revealing that this flexible extension becomes ordered upon inhibition through exchange between adjacent B-subunits. For human RAD52, the 2.2 Å cryo-EM map resolves the undecameric N-terminal ring and its hydration network. In parallel, SEC-SAXS combined with computational methods provides a comprehensive description of the highly flexible and dynamic organization of the C-terminal region of full-length RAD52, which remains largely unresolved in the cryo-EM reconstruction.