2GSK:
reference: Outer membrane active transport: structure of the BtuB:TonB complex., Shultis DD, Purdy MD, Banchs CN, Wiener MC, Science. 2006 Jun 2;312(5778):1396-9. PMID: 16741124

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