User:Brian Conner/Sandbox 1
From Proteopedia
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== Structure == | == Structure == | ||
| - | Conventionally elastin was thought to be an amorphous polypeptide but recent break studies and breakthroughs have lead to some speculation as to some of the possible structures that could be found in elastin. | + | Conventionally elastin was thought to be an amorphous polypeptide but recent break studies and breakthroughs have lead to some speculation as to some of the possible structures that could be found in elastin. Since the main function of elastin is to provide elasticity to the cell and surrounding tissue it would stand to reason that the protein would need to be very flexible. This would naturally lead to the conclusion that elastin must be glycine rich since this is the most flexible amino acid. Also elastin must have certain biophysical properties in order to provide the function of elasticity. Elastin must be able to be found in two different states; a relaxed state and a stretched state. The presence of or lack of water also helps to physically stabilize the system. |
| - | + | ||
| + | As shown in the table above, the theory behind the structure of elastin is based on the driving force of entropy. When an external force acts on the elastin to stretch it the entropy of the system is decreased, and when that external force is decreased or taken away then entropy drives elastin to recoil back to its relaxed state which has higher entropy. | ||
| + | |||
| + | Currently there are two groups working on solving the mystery of elastin's structure and each group has purposed models which share some similarities but also have some differences. The First group is the Birmingham (U.S.A.) group, on the basis of extensive studies on synthetic poly(VPGVG), a repeating sequence of elastin, introduced a structural model supporting a new mechanism of elasticity. With Urry’s model of poly(VPGVG), there is one type II β-turn per pentameric unit with PG at the corner of the bend and a 4→1 hydrogen bond connecting the CO group of the first valine to the NH of the fourth valine along the sequence. The repetition of this conformational unit gives rise to a helical arrangement called the β-spiral. The β-turns act as spacers between the turns of the spiral. | ||
| + | |||
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| + | == Function == | ||
| + | The main function of elastin is to provide elasticity to cells and the surrounding tissue. It is able to do this through its very flexible, stretchable, and when required rigid structure. | ||
== Disease == | == Disease == | ||
Deletions and mutations in the gene that encodes for elastin can result in supraventricular aortic stenosis, and autosomal dominant cutis laxa. Other disorders that are associated with defects in elastin are Marfan's Snydrome and emphysema, which is caused by an α<sub>1</sub>-antitrypsin deficiency. | Deletions and mutations in the gene that encodes for elastin can result in supraventricular aortic stenosis, and autosomal dominant cutis laxa. Other disorders that are associated with defects in elastin are Marfan's Snydrome and emphysema, which is caused by an α<sub>1</sub>-antitrypsin deficiency. | ||
== References == | == References == | ||
Revision as of 20:06, 1 May 2014
Elastin
Elastin is a fibrous protein that can be found in human connective tissue and gives the tissue its elastic quality. This allows tissues that have been stretched to regain their original shape. Elastin is typically found in tissue such as skin, blood vessels, lungs, and urinary. At the cellular level elastin is found in the extracellular matix. Mature elastin is an insoluble polymer constituted by several tropoelastin molecules covalently bound to each other by cross-links. These can be bi- (lysinonorleucine), tri- (merodesmosine) or tetra-functional (desmosine and isodesmosine) in nature, and the increase in complexity is thought to progress as the fiber matures and ages. Despite its very hydrophobic nature, elastin is highly hydrated by water that swells the polymer in vivo. Mature elastin is extremely stable, and its turnover is so slow it can be assumed that elastin lasts for the entire lifespan of the organism.
Contents |
Gene
The elastin gene is a single copy gene localized in chromosome 7 in humans and, under normal conditions, is expressed by various cell types during the pre- and neonatal stages of development. The elastin gene product, tropoelastin, is a protein of 750 to 800 residues. As a norm, the elastin gene possesses 36 exons, some of which code for hydrophobic sequences and others for lysine-containing segments. The introns of the human gene are much larger than the exons 3 and 32 and the exon–intron boundaries always split codons in the same manner. This unique feature allows extensive alternative splicing of the primary transcripts without disrupting the reading frame 32, 52, 53 and 83 and results in the translation of various tropoelastin isoforms. Recent results show that this phenomenon is spatially and developmentally regulated. Thus, it should have some functional significance but, to date, is not fully understood.
Structure
Conventionally elastin was thought to be an amorphous polypeptide but recent break studies and breakthroughs have lead to some speculation as to some of the possible structures that could be found in elastin. Since the main function of elastin is to provide elasticity to the cell and surrounding tissue it would stand to reason that the protein would need to be very flexible. This would naturally lead to the conclusion that elastin must be glycine rich since this is the most flexible amino acid. Also elastin must have certain biophysical properties in order to provide the function of elasticity. Elastin must be able to be found in two different states; a relaxed state and a stretched state. The presence of or lack of water also helps to physically stabilize the system.
As shown in the table above, the theory behind the structure of elastin is based on the driving force of entropy. When an external force acts on the elastin to stretch it the entropy of the system is decreased, and when that external force is decreased or taken away then entropy drives elastin to recoil back to its relaxed state which has higher entropy.
Currently there are two groups working on solving the mystery of elastin's structure and each group has purposed models which share some similarities but also have some differences. The First group is the Birmingham (U.S.A.) group, on the basis of extensive studies on synthetic poly(VPGVG), a repeating sequence of elastin, introduced a structural model supporting a new mechanism of elasticity. With Urry’s model of poly(VPGVG), there is one type II β-turn per pentameric unit with PG at the corner of the bend and a 4→1 hydrogen bond connecting the CO group of the first valine to the NH of the fourth valine along the sequence. The repetition of this conformational unit gives rise to a helical arrangement called the β-spiral. The β-turns act as spacers between the turns of the spiral.
Function
The main function of elastin is to provide elasticity to cells and the surrounding tissue. It is able to do this through its very flexible, stretchable, and when required rigid structure.
Disease
Deletions and mutations in the gene that encodes for elastin can result in supraventricular aortic stenosis, and autosomal dominant cutis laxa. Other disorders that are associated with defects in elastin are Marfan's Snydrome and emphysema, which is caused by an α1-antitrypsin deficiency.
