IRP2 deletion mutants lacking the C-terminal domain 4 are resistant to iron-dependent degradation. (A) Schematic representation of the deletion mutants showing domains 1–4, the hinge which links domains 3 and 4, and the C-terminal HA tag. The 73 amino acids sequence (73d) within domain 1 is highlighted in gray. (B-G) H1299 cells engineered to express wild type IRP2 or two independent clones of the above mutants (except ΔD1) were treated overnight (14 h) with 100 μM hemin or 30 μg/ml FAC and lysates were subjected to Western blotting with HA (top) and β-actin (bottom) antibodies. No clones expressing ΔD1 could be isolated.