The name/synonym for ligand HIS (curated from ChEBI, PubChem, and PDB databases):

1L-HISTIDINE
2(S)-ALPHA-AMINO-1H-IMIDAZOLE-4-PROPANOIC ACID
3HISTIDINE
4L-(-)-HISTIDINE
5(2S)-2-AMINO-3-(1H-IMIDAZOL-4-YL)PROPANOIC ACID
6L-HISTIDIN
7(S)-ALPHA-AMINO-1H-IMIDAZOLE-4-PROPIONIC ACID