5NB9:
reference: Structure of the Escherichia coli ProQ RNA-binding protein., Gonzalez GM, Hardwick SW, Maslen SL, Skehel JM, Holmqvist E, Vogel J, Bateman A, Luisi BF, Broadhurst RW, RNA. 2017 May;23(5):696-711. doi: 10.1261/rna.060343.116. Epub 2017 Feb 13. PMID: 28193673

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