English: Structure of human ApoD in complex with progesterone (adapted from Eichinger et al., 2007). Left: front view showing the 8 anti-parallel -strands (yellow) structure forming the hydrophobic cavity typical of the lipocalins. Loops A/B, C/D, E/F and G/H link the -strands at the open end of the protein. Other loops are present at the opposite end of the protein (white). There are 2 α-helix (purple) located close to the cavity, one of which is able to close the cavity. The two glycosylated residues (N45 and N78) are shown. The 2 disulfide bridges are not visible. Right: top view of the cavity showing the progesterone ligand (grey).