Protein Domain : Tropoelastin IPR003979

Type	Family
Description	Tropoelastin is the precursor to the elastin molecule. Elastin aggregates are responsible for the stretch properties of skin, arterial walls andligaments, and elastin is implicated in several hereditary diseases, including cutis laxa (where the elasticity of the skin is lost) andelastoderma (similar to cutis laxa but with grape-like accumulations of elastin in the dermis). The unusual and highly characteristic amino acidcomposition of this protein accounts for its great hydrophobicity. It contains one-third glycine amino acids and several lysine derivatives that serve as covalent cross-links between protein monomers. Elastin is thus a three-dimensional network with 60-70 amino acids between two cross-linking points. This moleculararchitecture is determinant for its elastic properties, insolubility and resistance to proteolysis.Normally, the elastin gene contains 36 exons, and this structure allows the formation of stable isoforms by alternative splicing. The 3-dimensionalstructure of elastin is currently unknown and was originally thought to be an amorphous polymer. This is consistent with the theory of rubberelasticity, which requires the resting state of the protein to be of higher disorder (entropy) than the extended state [].More recent studies show the presence of helical and other secondary structures [], and the elasticity theory has been amended to involve, inthe resting state, secondary structure elements in chaotic motion. In the extended state of the protein, the secondary structures align to form anordered structure together with neighbouring molecules [ ].Tropoelastin consists mainly of repetitive elements of four, five,six and nine hydrophobic residues []. The five, six and nine residue repeatsfunction as binding sites for fibroblasts during chemotaxis (the hexapeptide and nonapeptide repeats competing for the same receptor) []. Thehexapeptide repeat is also known to bind calcium ions. The formation of the elastin fibre is a complicated process, involving the binding of a chaperone to the precursor to prevent aggregation in the cell,followed by migration out of the cell, whereupon the chaperone disassociates. The tropoelastin molecules then cross-link to each otherusing deaminated lysine residues, the microfibril structures functioning as a scaffold [].
Short Name	Tropoelastin