1NWK:
reference: Crystal structure of monomeric actin in the ATP state. Structural basis of nucleotide-dependent actin dynamics., Graceffa P, Dominguez R, J Biol Chem 2003 Sep 5;278(36):34172-80. Epub 2003 Jun 17. PMID: 12813032

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