The tropoelastin is a protein of 60-72 kDa linked alternately, it is part of the extracellular matrix and soluble precursor of elastin . It is found in all vertebrates except for cyclostomes . The molecules tropoelastin behave as perfect elastic molecules that can be stretched and compressed repeatedly completely reversible processes.
Summary
[ hide ]
- 1 Features
- 2 Structure
- 3 Training
- 4 Sources
characteristics
Tropoelastine is a water soluble molecule with a molecular weight of approximately 72,000 daltons . Several tropoelastine molecules covalently bond together with crosslinks to form the protein elastin that is very prevalent in the body. There is only one gene for this molecule and therefore only one protein. However, occasional splicing provides tissue specificity .
There are 36 small domains in Tropoelastine and each weighs approximately 2 kilodaltons . Within exons , there are alternating hydrophobic and lysine- rich domains , this is important in elastin formation. Tropoelastine does not undergo cleavage and the formation of microfibrils is achieved through a self-association process called coacervation .
Structure
Human tropoelastine is encoded by a single gene that has 34 exons and gives rise to multiple isoforms . The mRNA encodes a 72 kDa polypeptide depending on the binding and removal pattern of a signal peptide , which leaves a mature protein with a molecular weight of at least 60KDa. At least 11 forms of binding of human tropoelastin have been characterized, resulting from a down-regulated alternative binding of domains 22, 23, 24, 26th, 32 and 33.
Tropoelastine is an asymmetric molecule with a gradual, spring-shaped spiral along the axial axis of the molecule. This spiral region accounts for much of the elasticity of tropoelastine. In addition to the spiral, the molecule has another dominant and functionally relevant part called the C-terminal. This is located at the foot of the molecule (region of cell contact) and contains two characteristic features: the only two cysteine residues.in the molecule they are very little separated in the final domain 36 and form a disulfide bond, while the protein ends in a positively charged RKRK sequence. Both disruption of disulfide bonds and removal of the C-terminal region reduce the ability of tropoelastine to be assembled into developing fibers, which can lead to severe disease states such as aortic supravalcular stenosis (SVAS).
The amino acid sequences that make up this molecule are divided into hydrophilic and hydrophobic domains. Hydrophobic domains are rich in nonpolar amino acids such as glycine , valine, and proline that typically appear in repetitive sequences. Alternating with these domains there are hydrophilic regions characterized by a high content of lysine and alanine and their contribution in cross-links.
Training
It is secreted by elastogenic cells, mainly smooth muscle cells and various fibroblasts. Tropoelastine self-assembles into consistent globules many microns in diameter that remain attached to the cell surface. This stage is the first step in the formation of elastic fibers.
Tropoelastine production is affected by age. Mammal formation occurs primarily during the fetal period and early infancy and stops at maturity. In case of damage, production of tropoelastin can be quickly reactivated and is influenced by factors such as necrosis of tumors , factor-α , interleukin 1β, growth factor insulin – like 1 and strongly by transforming growth factor.