A search for protein structures containing at least one of the metal ions of interest, magnesium (Mg 2+ ), manganese (Mn 2+ ) or zinc (Zn 2+ ), was conducted using PDB's Advanced Search Query Builder. The query included "protein only" as the entry polymer type (under structure attributes) and the metal ion as the chemical ID (MG, MN or ZN, under chemical attributes). The PDB structures found on September 22nd, 2023, were downloaded as .pdb.gz files using the shell script for batch download.