4FXI:
reference: The crystal structure of the intact E. coli RelBE toxin-antitoxin complex provides the structural basis for conditional cooperativity., Boggild A, Sofos N, Andersen KR, Feddersen A, Easter AD, Passmore LA, Brodersen DE, Structure. 2012 Oct 10;20(10):1641-8. doi: 10.1016/j.str.2012.08.017. Epub 2012, Sep 13. PMID: 22981948

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