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

1L-PROLINE
2L-PROLIN
3(S)-2-CARBOXYPYRROLIDINE
4(S)-2-PYRROLIDINECARBOXYLIC ACID
5PROLINA
6(2S)-PYRROLIDINE-2-CARBOXYLIC ACID
7(-)-PROLINE
8(S)-PYRROLIDINE-2-CARBOXYLIC ACID
9(-)-2-PYRROLIDINECARBOXYLIC ACID
10L-ALPHA-PYRROLIDINECARBOXYLIC ACID
11L-(-)-PROLINE
12L-PYRROLIDINE-2-CARBOXYLIC ACID
13PROLINUM
14(-)-(S)-PROLINE
15P
162-PYRROLIDINECARBOXYLIC ACID
17PROLINE