Apolipoprotein D is a protein that in humans is encoded by the APOD gene.
Unlike other lipoproteins, which are mainly produced in the liver, apolipoprotein D is mainly produced in the brain and testes.
It is a 29 kDa glycoprotein discovered in 1963 as a component of the High Density Lipoprotein (HDL) fraction of human plasma.
It is the major component of human mammary cyst fluid.
The human gene encoding it was cloned in 1986 and the deduced protein sequence revealed that ApoD is a member of the lipocalin family, small hydrophobic molecule transporters (Drayna et al, 1986).
ApoD is 169 amino acids long, including a secretion peptide signal of 20 amino acids.
It contains two glycosylation sites (aspargines 45 and 78) and the molecular weight of the mature protein varies from 20 to 32 kDa (see figure 1).

 The resolved tertiary structure shows that ApoD is composed of 8 anti-parallel β-strands forming a hydrophobic cavity capable of receiving different ligands.
ApoD also contains 5 cysteine residues, 4 of which are involved in intra-molecular disulfide bonds.
Apolipoprotein D is a protein that in humans is encoded by the APOD gene. Unlike other lipoproteins, which are mainly produced in the liver, apolipoprotein D is mainly produced in the brain and testes. It is a 29 kDa glycoprotein discovered in 1963 as a component of the High Density Lipoprotein (HDL) fraction of human plasma. It is the major component of human mammary cyst fluid. The human gene encoding it was cloned in 1986 and the deduced protein sequence revealed that ApoD is a member of the lipocalin family, small hydrophobic molecule transporters (Drayna et al, 1986). ApoD is 169 amino acids long, including a secretion peptide signal of 20 amino acids. It contains two glycosylation sites (aspargines 45 and 78) and the molecular weight of the mature protein varies from 20 to 32 kDa (see figure 1).
 The resolved tertiary structure shows that ApoD is composed of 8 anti-parallel β-strands forming a hydrophobic cavity capable of receiving different ligands. ApoD also contains 5 cysteine residues, 4 of which are involved in intra-molecular disulfide bonds.
Apolipoprotein D