<p>The green dashes indicate the hydrogen bonds formed. All the structures are shown in ball and stick. The amino acids were colored according to the atom type, i.e. green for carbon, red for oxygen, blue for nitrogen and white for hydrogen. Among the amino acids in the binding site, only E353, R394 and H524 are shown in this figure. E<sub>2</sub> was colored in white. The ligands were shown in the following different colors: in <b>panel A</b>, 6α-OH-E<sub>2</sub> (yellow), 6β-OH-E<sub>2</sub> (orange), 6-keto-E<sub>2</sub> (pink), 6-dehydro-E<sub>2</sub> (red), 7-dehydro-E<sub>2</sub> (magenta), 9(11)-dehydro-E<sub>2</sub> (light blue), 11α-OH-E<sub>2</sub> (purple) and 11 β-OH-E<sub>2</sub> (green); in <b>panel B</b>, E<sub>1</sub> (magenta) estriol (16α-OH-E<sub>2</sub>) (yellow), 16β-OH-E<sub>2</sub> (orange), 16-keto-E<sub>2</sub> (pink), 17α-OH-E<sub>2</sub> (red), 15α-OH-E<sub>3</sub> (dark blue), 16α-OH-E<sub>1</sub> (light blue), 16-keto-E<sub>1</sub> (purple), 16α-OH-E<sub>2</sub>-17α (brown), 16β-OH-E<sub>2</sub>-17α (grey).</p
