Elastin

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Elastin is a key protein of the extracellular matrix. Elastin_sentence_0

It is highly elastic and present in connective tissue allowing many tissues in the body to resume their shape after stretching or contracting. Elastin_sentence_1

Elastin helps skin to return to its original position when it is poked or pinched. Elastin_sentence_2

Elastin is also an important load-bearing tissue in the bodies of vertebrates and used in places where mechanical energy is required to be stored. Elastin_sentence_3

In humans, elastin is encoded by the ELN gene. Elastin_sentence_4

Function Elastin_section_0

The ELN gene encodes a protein that is one of the two components of elastic fibers. Elastin_sentence_5

The encoded protein is rich in hydrophobic amino acids such as glycine and proline, which form mobile hydrophobic regions bounded by crosslinks between lysine residues. Elastin_sentence_6

Multiple transcript variants encoding different isoforms have been found for this gene. Elastin_sentence_7

Elastin's soluble precursor is tropoelastin. Elastin_sentence_8

The characterization of disorder is consistent with an entropy-driven mechanism of elastic recoil. Elastin_sentence_9

It is concluded that conformational disorder is a constitutive feature of elastin structure and function. Elastin_sentence_10

Clinical significance Elastin_section_1

Deletions and mutations in this gene are associated with supravalvular aortic stenosis (SVAS) and the autosomal dominant cutis laxa. Elastin_sentence_11

Other associated defects in elastin include Marfan syndrome, emphysema caused by α1-antitrypsin deficiency, atherosclerosis, Buschke-Ollendorff syndrome, Menkes syndrome, pseudoxanthoma elasticum, and Williams syndrome. Elastin_sentence_12

Elastosis Elastin_section_2

Elastosis is the buildup of elastin in tissues, and is a form of degenerative disease. Elastin_sentence_13

There are a multitude of causes, but the most commons cause is actinic elastosis of the skin, also known as solar elastosis, which is caused by prolonged and excessive sun exposure, a process known as photoaging. Elastin_sentence_14

Uncommon causes of skin elastosis include elastosis perforans serpiginosa, perforating calcific elastosis and linear focal elastosis. Elastin_sentence_15

Elastin_table_general_0

Skin elastosis causesElastin_table_caption_0
ConditionElastin_header_cell_0_0_0 Distinctive featuresElastin_header_cell_0_0_1 HistopathologyElastin_header_cell_0_0_2
Actinic elastosis

(most common, also called solar elastosis)Elastin_header_cell_0_1_0

Elastin replacing collagen fibers of the papillary dermis and reticular dermisElastin_cell_0_1_1 Elastin_cell_0_1_2
Elastosis perforans serpiginosaElastin_header_cell_0_2_0 Degenerated elastic fibers and transepidermal perforating canals (arrow in image points at one of them)Elastin_cell_0_2_1 Elastin_cell_0_2_2
Perforating calcific elastosisElastin_header_cell_0_3_0 Clumping of short elastic fibers in the dermis.Elastin_cell_0_3_1 Elastin_cell_0_3_2
Linear focal elastosisElastin_header_cell_0_4_0 Accumulation of fragmented elastotic material within the papillary dermis and transcutaneous elimination of elastotic fibers.Elastin_cell_0_4_1 Elastin_cell_0_4_2

Composition Elastin_section_3

In the body, elastin is usually associated with other proteins in connective tissues. Elastin_sentence_16

Elastic fiber in the body is a mixture of amorphous elastin and fibrous fibrillin. Elastin_sentence_17

Both components are primarily made of smaller amino acids such as glycine, valine, alanine, and proline. Elastin_sentence_18

The total elastin ranges from 58 to 75% of the weight of the dry defatted artery in normal canine arteries. Elastin_sentence_19

Comparison between fresh and digested tissues shows that, at 35% strain, a minimum of 48% of the arterial load is carried by elastin, and a minimum of 43% of the change in stiffness of arterial tissue is due to the change in elastin stiffness. Elastin_sentence_20

Tissue distribution Elastin_section_4

Elastin serves an important function in arteries as a medium for pressure wave propagation to help blood flow and is particularly abundant in large elastic blood vessels such as the aorta. Elastin_sentence_21

Elastin is also very important in the lungs, elastic ligaments, elastic cartilage, the skin, and the bladder. Elastin_sentence_22

It is present in all vertebrates above the jawless fish. Elastin_sentence_23

Characteristics Elastin_section_5

Elastin is a very long-lived protein, with a half-life of over 78 years in humans. Elastin_sentence_24

Clinical research Elastin_section_6

The feasibility of using recombinant human tropoelastin to enable elastin fiber production to improve skin flexibility in wounds and scarring has been studied. Elastin_sentence_25

After subcutaneous injections of recombinant human tropoelastin into fresh wounds it was found there was no improvement in scarring or the flexibility of the eventual scarring. Elastin_sentence_26

Biosynthesis Elastin_section_7

Tropoelastin precursors Elastin_section_8

Elastin is made by linking together many small soluble precursor tropoelastin protein molecules (50-70 kDa), to make the final massive insoluble, durable complex. Elastin_sentence_27

The unlinked tropoelastin molecules are not normally available in the cell, since they become crosslinked into elastin fibres immediately after their synthesis by the cell and during their export into the extracellular matrix. Elastin_sentence_28

Each tropoelastin consists of a string of 36 small domains, each weighing about 2 kDa in a random coil conformation. Elastin_sentence_29

The protein consists of alternating hydrophobic and hydrophilic domains, which are encoded by separate exons, so that the domain structure of tropoelastin reflects the exon organization of the gene. Elastin_sentence_30

The hydrophilic domains contain Lys-Ala (KA) and Lys-Pro (KP) motifs that are involved in crosslinking during the formation of mature elastin. Elastin_sentence_31

In the KA domains, lysine residues occur as pairs or triplets separated by two or three alanine residues (e.g. AAAKAAKAA) whereas in KP domains the lysine residues are separated mainly by proline residues (e.g. KPLKP). Elastin_sentence_32

Aggregation Elastin_section_9

Tropoelastin aggregates at physiological temperature due to interactions between hydrophobic domains in a process called coacervation. Elastin_sentence_33

This process is reversible and thermodynamically controlled and does not require protein cleavage. Elastin_sentence_34

The coacervate is made insoluble by irreversible crosslinking. Elastin_sentence_35

Crosslinking Elastin_section_10

To make mature elastin fibres, the tropoelastin molecules are cross-linked via their lysine residues with desmosine and isodesmosine cross-linking molecules. Elastin_sentence_36

The enzyme that performs the crosslinking is lysyl oxidase, using an in vivo Chichibabin pyridine synthesis reaction. Elastin_sentence_37

Molecular biology Elastin_section_11

In mammals, the genome only contains one gene for tropoelastin, called ELN. Elastin_sentence_38

The human ELN gene is a 45 kb segment on chromosome 7, and has 34 exons interrupted by almost 700 introns, with the first exon being a signal peptide assigning its extracellular localization. Elastin_sentence_39

The large number of introns suggests that genetic recombination may contribute to the instability of the gene, leading to diseases such as SVAS. Elastin_sentence_40

The expression of tropoelastin mRNA is highly regulated under at least eight different transcription start sites. Elastin_sentence_41

Tissue specific variants of elastin are produced by alternative splicing of the tropoelastin gene. Elastin_sentence_42

There are at least 11 known human tropoelastin isoforms. Elastin_sentence_43

these isoforms are under developmental regulation, however there are minimal differences among tissues at the same developmental stage. Elastin_sentence_44

See also Elastin_section_12

Elastin_unordered_list_0


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Elastin.