Tropoelastins

Tropoelastins are the soluble precursor molecules that polymerize to form elastin, a key component of elastic fibers in the extracellular matrix. They are produced mainly by fibroblasts and smooth muscle cells and are encoded by the ELN gene. After secretion into the extracellular space, tropoelastin monomers assemble into insoluble elastin through crosslinking, contributing to the elastic properties of tissues such as skin, lungs, arteries, and ligaments.

Structurally, tropoelastin consists of alternating hydrophobic and crosslinking domains. The hydrophobic segments promote elasticity, while lysine-rich regions provide sites for covalent crosslinking. Crosslinking is initiated by lysyl oxidase, which converts certain lysine residues to reactive aldehydes that form desmosine and related desmosine-like crosslinks between tropoelastin molecules, stabilizing the elastin polymer within elastic fibers.

Biogenesis and assembly involve secretion of tropoelastin, its coacervation (a temperature-dependent self-assembly process), and subsequent deposition onto a scaffold of microfibrils, principally composed of fibrillin-1. Elastin fibers then mature through further crosslinking and interaction with elastin-binding proteins, producing an elastic network capable of rapid and repeated stretch and recoil.

Functionally, elastin provides resilience and recoil to tissues, allowing them to resume shape after deformation. Elastic fibers are abundant in tissues subjected to repeated mechanical strain and contribute to vascular compliance, lung ventilation, and skin tability. Tropoelastin expression is regulated developmentally and by mechanical and biochemical cues; aging and disease can affect elastin content and elasticity.

Clinical relevance includes elastin gene (ELN) mutations linked to connective tissue disorders such as cutis laxa and supravalvular aortic stenosis, highlighting elastin’s essential role in tissue elasticity and integrity.