4AL6:
reference: Csy4 relies on an unusual catalytic dyad to position and cleave CRISPR RNA., Haurwitz RE, Sternberg SH, Doudna JA, EMBO J. 2012 Apr 20. doi: 10.1038/emboj.2012.107. PMID: 22522703

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