Which of the following factors gives the elastin molecule the ability to stretch and recoil?
1.Hydroxylation of proline and lysine rich regions
2.Cross-links between lysine residues
4.Triple helix formation
5.Cleavage of disulfide rich terminal regions
Elastin is an elastic protein found in lungs, dermis, large arteries, ligaments, vocal cords, and the ligamentum flavum. Its ability to stretch is conferred by interchain crosslinks between lysine residues.
Similar to collagen, elastin is synthesized in several steps. It begins as a large precursor molecule, tropoelastin. Tropoelastin is secreted into the extracellular matrix, where it interacts with fibrillin-containing microfibril scaffolds to form elastic fibers. The lysine residues on separate elastin molecules interact in a process called desmosine cross-chain linking, providing elastin with its stretch.
Rucker and Dubick provide a review of the structure and synthesis of elastin. They note that lysine residues are not hydroxylated in elastin, while they are hydroxylated in collagen. They describe the desmosine cross-links that form between lysine residues as necessary in order to restrict the stretch of elastic fibers and allow realignment and re-organization when the elastic fiber is no longer under tension.
Dewar and Curry review diagnosis and management of COPD. Elastin is a large component of the lung and loss of alpha-1-antitrypsin (A1AT) inhibition of elastase may lead to emphysema in those affected with alpha-1-antitrypsin deficiency. The authors recommend testing for A1AT deficiency in patients who develop emphysema despite never smoking, those with family history of disease, those with lower-lung emphysema, or early onset emphysema.
Illustration A is a diagram of the steps in elastic fiber formation.
Illustration B shows the relationship between microfibrils and elastic fiber formation.