6H9D:
reference: Origin of a Core Bacterial Gene via Co-option and Detoxification of a Phage Lysin., Randich AM, Kysela DT, Morlot C, Brun YV, Curr Biol. 2019 May 20;29(10):1634-1646.e6. doi: 10.1016/j.cub.2019.04.032. Epub , 2019 May 9. PMID: 31080080

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