6IQG:
reference: Site-specific chemical conjugation of antibodies by using affinity peptide for the development of therapeutic antibody format., Kishimoto S, Nakashimada Y, Yokota R, Hatanaka T, Adachi M, Ito Y, Bioconjug Chem. 2019 Jan 4. doi: 10.1021/acs.bioconjchem.8b00865. PMID: 30606013

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