Tropoelastiinit

Tropoelastin is the soluble precursor protein that polymerizes to form elastin, the key component of elastic fibers in connective tissue. In humans it is encoded by the ELN gene, located on chromosome 7q11.23. Tropoelastin is produced by elastogenic cells such as fibroblasts and vascular smooth muscle cells and is secreted into the extracellular space where it participates in elastogenesis.

Tropoelastin monomers are secreted with an N-terminal signal peptide and undergo coacervation, a temperature- and pH-dependent self-assembly process that concentrates the protein and facilitates deposition onto a scaffold of microfibrils, including fibrillin-1. Cross-linking by lysyl oxidase forms covalent desmosine and isodesmosine bonds that stabilize the mature elastin network.

Tropoelastin has a length of roughly 700-800 amino acids and comprises alternating hydrophobic domains and lysine-rich cross-linking regions. The hydrophobic segments drive coacervation and elasticity; the cross-linking domains provide sites for covalent cross-links that give elastin its resilience. Mature elastin fibers are long-lived and have low intrinsic turnover, especially in adulthood.

Functionally, elastin provides elasticity and recoil to skin, lungs, arteries, ligaments, and other tissues. Its integrity is crucial for normal vessel compliance and tissue mechanics. Elastin synthesis can occur during development and tissue remodeling; age-related degradation reduces elastic fiber content.

Clinical significance: ELN mutations or haploinsufficiency cause connective tissue disorders such as supravalvular aortic stenosis and cutis laxa. Aberrant tropoelastin biogenesis is implicated in various vascular and dermal pathologies.