The Lipocalin family is composed of structurally conserved hydrophobic ligand binding proteins and is represented in all major taxonomic groups from prokaryotes to primates. Members of the lipocalin family are characterized by several common molecular-recognition properties: the ability to bind a range of small hydrophobic molecules, binding to specific cell-surface receptors and the formation of complexes with soluble macromolecules. Lipocalin-6, also known as LCN5, hLcn5, UNQ643 or LCN6, is a 163 amino acid protein that is predominantly expressed in epididymis. Lipocalin-6 locatizes to the head and tail of spermatozoa, with the highest concentration on the post-acrosomal region of the head. Belonging to the calycin superfamily, Lipocalin-6 may play a role in sperm maturation. The gene encoding Lipocalin-6 maps to human chromosome 9, which houses over 900 genes and comprises nearly 4% of the human genome.