Elastin

Elastin is a fibrillar, elastic structural protein that is close to collagen and is found in most vertebrates.

Elastin is the main component of the elastic fibres of connective tissue. Elastin is made up of long, coiled polypeptide chains cross-linked by desmosin (condensation product of the amino acid lysine). This network structure determines the elasticity of the structural protein. The building blocks are glycine, alanine, valine, proline, leucine and isoleucine. They are present in the repeating partial sequence Gly-Gly-Val-Pro and Gly-Val-Pro-Gly. In vertebrate organisms, elastin is mainly found in organs in which elastic properties are of great functional importance, such as the lungs, skin and blood vessels. In particular, elastin in elastic fibres is responsible for the stretchability of large blood vessels (e.g. the aorta).

Elastin is secreted by fibroblasts in a soluble, non-cross-linked form (tropoelastin) and then cross-linked by the enzyme lysyl oxidase (LOX). The amino acid lysine is responsible for this cross-linking.

Copper deficiency and mutations in the LOX gene (The LOX gene, chromosome 5 gene locus q23.3-q31.2, encodes lysyl oxidase) can lead to a reduction in the enzyme activity of lysyl oxidase and to cutis laxa.

Mutations in the elastin gene (chromosome 7q11.23) cause disorders of elastin. The associated clinical pictures are autosomal dominant cutis laxa (ADCL) and supravalvular aortic stenosis (SVAS).

The physical property "elasticity" distinguishes the structural protein elastin from the related structural protein collagen. Due to the close bond between collagen and elastin in tissues (e.g. in large vessels), both elastic and tear-resistant properties are mediated.

Histologically, elastin can be represented by the Elastica van Gieson staining (EvG staining).

Elastin is a very durable protein with a half-life of > 70 years. The formation of elastin begins before birth and is only continued in the first years of life.

In the skin, the elastic fibres are responsible for the skin's state of tension. UV rays have been proven to damage elastin. It is transformed into a homogeneously clumsy material(elastosis). The (irreversible) UV-induced elastotic degeneration of elastin in the skin is called actinic elastosis. It causes loss of elasticity and wrinkling of the skin.

Elastin has a high resistance to most proteases. The proteases that can split elastin are called elastases. They can break down elastin and other scleroproteins, e.g. collagen type I, II, III, IV, VIII, IX, X and XI, as well as structural glycoproteins. Physiological counterparts are alpha1-antitrypsin and alpha2-macroglobulin. If the amount of alpha1-antitrypsin is insufficient, the elastase has a destructive effect (e.g. in pulmonary emphysema). Other diseases in which neutrophil elastase appears to play a significant role are cystic fibrosis, adult respiratory distress syndrome (ARDS), rheumatoid arthritis and infectious diseases.