1VPT:
reference: The 1.85 A structure of vaccinia protein VP39: a bifunctional enzyme that participates in the modification of both mRNA ends., Hodel AE, Gershon PD, Shi X, Quiocho FA, Cell 1996 Apr 19;85(2):247-56. PMID: 8612277

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