Elastin is a highly elastic protein in connective tissue and allows many tissues in the body to continue in shape after stretching or contraction. Elastin helps the skin to return to its original position when punctured or pinched. Elastin is also a network of important loads in the body of vertebrates and is used in places where mechanical energy is required to be stored. In humans elastin is encoded by the ELN genes.
Video Elastin
Function
The ELN gene encodes a protein that is one of two elastic fiber components. The encoded proteins are rich in hydrophobic amino acids such as glycine and proline, which form a mobile hydrophobic region bounded by a cross between lysine residues. Various transcriptional variants encoding various isoforms have been found for this gene. Elastin soluble precursor is tropoelastin. The characterization of the disturbance is consistent with the mechanism of elastic retraction driven by entropy. It was concluded that conformational disorder is a constitutive feature of elastin structure and function.
Maps Elastin
Clinical interests
Removal and mutation in these genes is associated with supravalvular aortic stenosis (SVAS) and dominant autosomal cutis laxa. Other abnormalities associated with elastin include Marfan syndrome, emphysema due to deficiency <1> -antitripsin, atherosclerosis, Buschke-Ollendorff syndrome, Menkes syndrome, pseudoxanthoma elasticum, and Williams syndrome.
Composition
In the body, elastin is usually associated with other proteins in connective tissue. The elastic fiber in the body is a mixture of amorphous elastin and fibrous fibrous. Both components are mainly made of smaller amino acids such as glycine, valine, alanine, and proline. Total elastin ranges from 58-75% of the weight of the fat-removed dry arteries in normal canine arteries. Comparisons between fresh and digested tissues show that, at 35% strain, at least 48% of the burden of the arteries is carried by elastin, and at least 43% of the stiffness of the arterial tissue is due to elastin stiffness change.
Network distribution
Elastin serves an important function in the arteries as a medium for pressure wave propagation to aid blood flow and is especially abundant in large elastic blood vessels such as the aorta. Elastin is also very important in the lungs, elastic ligaments, elastic cartilage, skin, and bladder. It exists in all vertebrates above the jawless fish.
Biosynthesis
Tropoelastin Precursor
Elastin is made by linking many molecular protein molecules to a soluble tropoelastin (50-70 kDa) precursor, to create a highly soluble and long lasting complex. Unrestricted tropoelastin molecules are usually not available in cells, as they cross into elastin fibers immediately after their synthesis by cells and during their export to the extracellular matrix.
Each tropoelastin consists of a string of 36 small domains, each weighing about 2 kDa in a random coil conformation. Proteins consist of alternating hydrophobic and hydrophilic domains, which are encoded by separate exons, so the tropoelastin domain structure reflects the organization of the exon genes. The hydrophilic sphere contains Lys-Ala (KA) and Lys-Pro (KP) motifs involved in crosslinking during the formation of mature elastin. In the rail domain, lysine residues occur as pairs or triplets separated by two or three alanine residues (eg AAAKAAKAA) whereas in the KP domain the lysine residue is separated primarily by prolin residues (eg KPLKP).
Aggregation
Aggregate tropoelastin at physiological temperature due to interaction between hydrophobic domains in a process called coacervation. This process is reversible and thermodynamically controlled and does not require protein cleavage. Coacervate is made insoluble by irreversible crosslinking.
Crosslinking
To make the elastin fibers mature, the tropoelastin molecules are crosslinked through their lysine residues with crosslinked molecules of desmosin and isodmosin. The crosslinking enzyme is lysil oxidase, using a chichibabin pyridine synthesis reaction in the in vivo reaction .
Molecular biology
In mammals, the genome contains only one gene for tropoelastin, called ELN . The human gene ELN is a 45 kb segment on chromosome 7, and has 34 exons disturbed by nearly 700 introns, with the first exone being a signal peptide that places its extracellular localization. A large number of introns suggest that genetic recombination may contribute to gene instability, leading to diseases such as SVAS. The phrase tropoelastin mRNA is highly regulated under at least eight different transcriptional start sites.
Tissue-specific elastin variants are produced by alternative splicing of the tropoelastin gene. There are at least 11 known human tropoelastin isoforms. this isoform is under developmental regulation, but there is minimal difference between networks at the same stage of development.
See also
- Elastic fibers
- Elastin Receptors
- Cutis laxa
- Williams Syndrome
References
Further reading
External links
- Elastin at the US National Library of Medicine's Medical Subject Headings (MeSH)
- Histology: 21402a - Histology Learning System at Boston University
- GeneReviews/NIH/NCBI/UW entered in Williams or Williams-Beuren Syndrome
- The Elastin Protein
- Microfibril
This article combines text from the National Medical Library of the United States, which is in the public domain.
Source of the article : Wikipedia
0 Comments