3PGF:
reference: Allosteric control of ligand-binding affinity using engineered conformation-specific effector proteins., Rizk SS, Paduch M, Heithaus JH, Duguid EM, Sandstrom A, Kossiakoff AA, Nat Struct Mol Biol. 2011 Apr;18(4):437-42. Epub 2011 Mar 6. PMID: 21378967

This OCA Structure page
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