1P9S:
reference: Coronavirus main proteinase (3CLpro) structure: basis for design of anti-SARS drugs., Anand K, Ziebuhr J, Wadhwani P, Mesters JR, Hilgenfeld R, Science 2003 Jun 13;300(5626):1763-7. Epub 2003 May 13. PMID: 12746549

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