6GA0:
reference: Crystal structure of a thermophilic O(6)-alkylguanine-DNA alkyltransferase-derived self-labeling protein-tag in covalent complex with a fluorescent probe., Rossi F, Morrone C, Massarotti A, Ferraris DM, Valenti A, Perugino G, Miggiano R, Biochem Biophys Res Commun. 2018 Jun 7;500(3):698-703. doi:, 10.1016/j.bbrc.2018.04.139. Epub 2018 Apr 30. PMID: 29684348

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