Interaction of E2 with human ERα and the 3D model lamprey ER.

<p>A. Interaction between E2 and human ERα. B. Interaction between E2 and the 3D model of lamprey ER. Lamprey ER has stabilizing interactions with the A ring of E2 similar to those in human ERα. His-509 has rotated and does not have a hydrogen bond with the C17-hydroxyl on E2. Instead, Cδ2 has a van der Waals contact with the C17-hydroxyl on E2. Also, Cε and Sδ on Met-409 have stabilizing contacts with C15 on E2.