3H4R:
reference: Crystal structure of E. coli RecE protein reveals a toroidal tetramer for processing double-stranded DNA breaks., Zhang J, Xing X, Herr AB, Bell CE, Structure. 2009 May 13;17(5):690-702. PMID: 19446525

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