6VXJ:
reference: ABCG2 transports anticancer drugs via a closed-to-open switch., Orlando BJ, Liao M, Nat Commun. 2020 May 8;11(1):2264. doi: 10.1038/s41467-020-16155-2. PMID: 32385283

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