4A0S:
reference: Unusual carbon fixation gives rise to diverse polyketide extender units., Quade N, Huo L, Rachid S, Heinz DW, Muller R, Nat Chem Biol. 2011 Dec 4;8(1):117-24. doi: 10.1038/nchembio.734. PMID: 22138621

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