Role of the HSPA9/HSC20 chaperone pair in promoting directional human iron-sulfur cluster exchange involving monothiol glutaredoxin 5

Cluster exchange chemistry for human glutaredoxin 5 (GLRX5) reveals distinct behavior from bacterial homologs with chaperones inhibiting rather than promoting cluster transfer from the iron‑sulfur cluster scaffold protein ISCU1, and controlling the directionality of transfer. Human iron‑sulfur cluster carrier protein NFU1 is identified as the most likely donor to GLRX5.112