4PCU:
reference: Structural insight into the molecular mechanism of allosteric activation of human cystathionine beta-synthase by S-adenosylmethionine., Ereno-Orbea J, Majtan T, Oyenarte I, Kraus JP, Martinez-Cruz LA, Proc Natl Acad Sci U S A. 2014 Sep 16;111(37):E3845-52. doi:, 10.1073/pnas.1414545111. Epub 2014 Sep 2. PMID: 25197074

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