5HK5:
reference: Structure of Gremlin-2 in Complex with GDF5 Gives Insight into DAN-Family-Mediated BMP Antagonism., Nolan K, Kattamuri C, Rankin SA, Read RJ, Zorn AM, Thompson TB, Cell Rep. 2016 Aug 23;16(8):2077-86. doi: 10.1016/j.celrep.2016.07.046. Epub 2016, Aug 11. PMID: 27524626

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