3PPQ:
reference: Structures of the substrate-binding protein provide insights into the multiple compatible solutes binding specificities of Bacillus subtilis ABC transporter OpuC., Du Y, Shi WW, He YX, Yang YH, Zhou CZ, Chen Y, Biochem J. 2011 Mar 3. PMID: 21366542

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