1PYK:
reference: Crystal structure of cat muscle pyruvate kinase at a resolution of 2.6 A., Stuart DI, Levine M, Muirhead H, Stammers DK, J Mol Biol 1979 Oct 15;134(1):109-42. PMID: 537059

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