Lipokaline

Lipokalins are a large, inhomogeneous family of small (molecular weight of 16-22kDa), inhomogeneous proteins that occur everywhere in nature, including animals, plants and bacteria. Lipokalins are involved in a variety of biological processes in the animal organism, such as the transport and storage of poorly soluble substances.

Lipokalins are characterized by a common tertiary structure consisting of an eight-stranded beta-sheet that forms an internal binding pocket. Despite the common tertiary structure, the amino acid sequences of the individual lipocalins are very different. The amino acid identities are often only 20%.

Lipokalins play a role in the regulation of the immune response, including the defence against pathogens in body fluids (e.g. in tear fluid). The amino acid acid densities are only 20%. Various lipokalins are excreted in the urine; they are ascribed a role in social behaviour as they transport pheromones and fragrances.

Another group of lipokalins with a high amino acididicity is an important source of allergens in fur animals and is responsible for cross-allergies between fur animals.

Most animal allergens belong to the protein family of lipokalins. Serum albumin is another family.

There is evidence that a sub-group of lipokalins has a relatively high amino acid identity of 47-67%. They can also cause cross-reactions. Many lipokalins are assigned a role in social maintenance, as they transport pheromones and fragrances.

1. Hilger C et al (2015) Male-specific submaxillary gland protein, a lipocalin allergen of the golden hamster, differs from the lipocalin allergens of Siberian and Roborovski dwarf hamsters. Int Arch Allergy Immunol 166:30-40.
2. Jensen-Jarolim E et al (2016) Structural similarities of human and mammalian lipocalins, and their function in innate immunity and allergy. Allergy 71:286-294.
3. Rytkönen-Nissinen M et al (2015) IgE Reactivity of the Dog Lipocalin Allergen Can f 4 and the Development of a Sandwich ELISA for Its Quantification. Allergy Asthma Immunol Res 7:384-392.
4. Roth-Walter Fet al. (2014) Bet v 1 from birch pollen is a lipocalin-like protein acting as allergen only when devoid of iron by promoting Th2 lymphocytes. J Biol Chem 289:17416-17421.