Elastin

Elastin (soluble precursor: tropoelastin ) is a fibrous protein found in vertebrates. It belongs to the structural proteins, because it is responsible in his capacity for shaping and support, in particular, it provides the ability to stretch large blood vessels such as the aorta. Mutations in the ELN gene can cause hereditary diseases, such as cutis laxa, Williams -Beuren syndrome and congenital subvalvular aortic stenosis ( SVAS ).

The composition is similar to those of elastin by collagen, but however, does not contain hydroxylysine, but a substantial proportion of valine (15.6%). Lysine residues can be oxidized by the enzyme lysyl oxidase to Allysin ( EC 1.4.3.13 ). Each 3 allysine and lysine may be converted into an annular desmosine, which contributes to the elasticity of the whole molecule.

Elastin is a protein network and consists of cross-linked elastin units. Elastin is secreted from the cells in a soluble form, and then cross-linked by the enzyme lysyl oxidase (LOX ). The amino acid lysine is responsible for this cross-linking.

In contrast to collagen elastin is elastically stretchable. Elastin occurs frequently in the lung, skin and blood vessels, and provides these flexibility.

Structure

Elastin is mainly composed of two different domains:

  • Hydrophobic domains, which are composed of repeating units of the amino acids glycine (G), valine (V), proline (P) and alanine (A). Frequent repetition units are, for example VPGVG, GGVP or GVGVAP.
  • Hydrophilic domains that are typically rich in lysine (K ), proline, and alanine. These domains are required for cross-linking. They consist of areas in which a lysin from the next are separated by two or three alanines, e.g. AAAKAAKAA or where lysine is located next to proline.

Elastin is comprised of alternating hydrophilic and hydrophobic domains, and has a molecular mass of approximately 72 kDa.

Metabolism and synthesis

Soluble elastin is secreted by various cells, cross-linked immediately after the exit of the cell into the extracellular matrix to elastin. The crosslinking is done by the copper - dependent enzyme lysyl oxidase, which oxidises the ε -amino groups of lysine with the release of hydrogen peroxide and ammonia. This results in a α - amino adipic semialdehyde δ. This can crosslink with another free amine to a Lysinonorleucin.

Because tropoelastin is crosslinked in vivo very fast, it is available only in extremely low concentrations in the tissue. The detection of tropoelastin was achieved by raising animals in which the production was inhibited by active lysyl oxidase.

Protein isoform Human Genome Organisation Dermatochalasis Lysyloxidase
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