Fig. 1: The recognition of trimethyllysine by the KDM5A PHD3 finger.

a View from the complex of the KDM5A PHD3 finger (pink) with H3K4me3 histone peptide (yellow) (PDB: 2KGI); b Structures of tryptophan and fluorinated tryptophan residues for probing the strength of cation–π interactions.