2PFU:
reference: The solution structure of the periplasmic domain of the TonB system ExbD protein reveals an unexpected structural homology with siderophore-binding proteins., Garcia-Herrero A, Peacock RS, Howard SP, Vogel HJ, Mol Microbiol. 2007 Oct 10;. PMID: 17927700

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