lipocalin


lipocalin

Any of a ubiquitous (found in plants, gram-negative bacteria, invertebrates and vertebrates) superfamily of carrier proteins, which share regions of sequence homology and a common tertiary structure: an eight-stranded, antiparallel, symmetrical beta-barrel fold (in essence, a beta sheet rolled into a cylinder enclosing an internal ligand binding site). Lipocalins transport small hydrophobic molecules (e.g., steroids, bilins, retinoids and lipids) and are associated with various biological processes, including immune response, pheromone transport, prostaglandin synthesis, retinoid binding and cancer cell interactions.
Human lipocalins
Alpha-1-microglobulin, alpha-1-acid glycoprotein (orosomucoid), aphrodisin, apolipoprotein D, beta-lactoglobulin, complement component C8 gamma chain, epididymal-retinoic acid binding protein, human pregnancy-associated endometrial alpha-2 globulin, probasin (a prostatic protein), prostaglandin D synthase.