Citrullination at the Nuclear Localization Signal of the Inhibitor of Growth 4 (ING4) Interferes With its Binding to Importin α3

H NMR experiments. All the peptides were capable of binding to PADI4 with low micromolar affinities, but their affinity decreased as the fraction of citrullination increased. Moreover, all peptides could bind to both importin species with affinities in the low micromolar range, and their affinities were also dependent on the citrullination degree. The peptides targeted the canonical NLS binding site for cargo proteins of both importin species. These findings suggest that: (i) citrullination at the NLS might interfere with ING4 nuclear translocation; and (ii) successive citrullination at the NLS affected binding to PADI4.