4RLR:
reference: The structure of PccH from Geobacter sulfurreducens: A novel low reduction potential monoheme cytochrome essential for accepting electrons from an electrode., Dantas JM, Campelo LM, Duke NE, Salgueiro CA, Pokkuluri PR, FEBS J. 2015 Mar 18. doi: 10.1111/febs.13269. PMID: 25786707

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).