The molecule is the porphyrin carboxylic acid anion that is ferroheme a protonated to pH 7.3. It is a conjugate base of a ferroheme a.
3-[18-(2-carboxylatoethyl)-7-ethenyl-17-formyl-12-[(1S,4E,8E)-1-hydroxy-5,9,13-trimethyltetradeca-4,8,12-trienyl]-3,8,13-trimethylporphyrin-21,23-diid-2-yl]propanoate;iron(2+)