2FYR:
reference: X-ray crystallographic structure of the Norwalk virus protease at 1.5-A resolution., Zeitler CE, Estes MK, Venkataram Prasad BV, J Virol. 2006 May;80(10):5050-8. PMID: 16641296

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