3A2I:
reference: Structural basis of the histidine-mediated vitamin D receptor agonistic and antagonistic mechanisms of (23S)-25-dehydro-1alpha-hydroxyvitamin D(3)-26,23-lactone., Kakuda S, Ishizuka S, Eguchi H, Mizwicki MT, Norman AW, Takimoto-Kamimura M, Acta Crystallogr D Biol Crystallogr. 2010 Aug;66(Pt 8):918-26. Epub 2010, Jul 10. PMID: 20693691

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