2GTB:
reference: Crystal Structures Reveal an Induced-fit Binding of a Substrate-like Aza-peptide Epoxide to SARS Coronavirus Main Peptidase., Lee TW, Cherney MM, Liu J, James KE, Powers JC, Eltis LD, James MN, J Mol Biol. 2007 Feb 23;366(3):916-32. Epub 2006 Dec 2. PMID: 17196984

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