2HZL:
reference: Crystal structures of an Extracytoplasmic Solute Receptor from a TRAP transporter in its open and closed forms reveal a helix-swapped dimer requiring a cation for alpha-keto acid binding., Gonin S, Arnoux P, Pierru B, Lavergne J, Alonso B, Sabaty M, Pignol D, BMC Struct Biol. 2007 Mar 15;7:11. PMID: 17362499

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