4OHS:
reference: The structure of a far-red fluorescent protein, AQ143, shows evidence in support of reported red-shifting chromophore interactions., Wannier TM, Mayo SL, Protein Sci. 2014 Jun 3. doi: 10.1002/pro.2498. PMID: 24888769

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