Fibrillin is a
glycoprotein
Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known a ...
, which is essential for the formation of
elastic fiber
Elastic fibers (or yellow fibers) are an essential component of the extracellular matrix composed of bundles of proteins (elastin) which are produced by a number of different cell types including fibroblasts, endothelial, smooth muscle, and ai ...
s found in
connective tissue
Connective tissue is one of the four primary types of animal tissue, a group of cells that are similar in structure, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesod ...
.
Fibrillin is secreted into the
extracellular matrix
In biology, the extracellular matrix (ECM), also called intercellular matrix (ICM), is a network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide structural and bio ...
by
fibroblasts
A fibroblast is a type of biological cell typically with a spindle shape that synthesizes the extracellular matrix and collagen, produces the structural framework ( stroma) for animal tissues, and plays a critical role in wound healing. Fibrobla ...
and becomes incorporated into the insoluble
microfibrils, which appear to provide a scaffold
for deposition of
elastin
Elastin is a protein encoded by the ''ELN'' gene in humans and several other animals. Elastin is a key component in the extracellular matrix of gnathostomes (jawed vertebrates). It is highly Elasticity (physics), elastic and present in connective ...
.
Clinical aspects
Marfan syndrome
Marfan syndrome (MFS) is a multi-systemic genetic disorder that affects the connective tissue. Those with the condition tend to be tall and thin, with dolichostenomelia, long arms, legs, Arachnodactyly, fingers, and toes. They also typically ha ...
is a genetic disorder of the connective tissue caused by defected
FBN1 gene. Mutations in
FBN1 and
FBN2 are also sometimes associated with
adolescent idiopathic scoliosis.
Types
Fibrillin-1
Fibrillin-1 is a major component of the
microfibrils that form a sheath surrounding the amorphous
elastin
Elastin is a protein encoded by the ''ELN'' gene in humans and several other animals. Elastin is a key component in the extracellular matrix of gnathostomes (jawed vertebrates). It is highly Elasticity (physics), elastic and present in connective ...
. It is believed that the
microfibrils are composed of end-to-end
polymer
A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...
s of fibrillin. To date, 3 forms of fibrillin have been described. The fibrillin-1 protein was isolated by Engvall in 1986,
and mutations in the FBN1 gene cause
Marfan syndrome
Marfan syndrome (MFS) is a multi-systemic genetic disorder that affects the connective tissue. Those with the condition tend to be tall and thin, with dolichostenomelia, long arms, legs, Arachnodactyly, fingers, and toes. They also typically ha ...
.
This protein is found in humans, and its gene is found on chromosome 15. At present more than 1500 different mutations have been described.
Structure
There is no complete, high-resolution structure of fibrillin-1. Instead, short fragments have been produced recombinantly and their structures solved by X-ray crystallography or using NMR spectroscopy. A recent example is the structure of the fibrillin-1 hybrid2 domain, in context of its flanking calcium binding epidermal growth factor domains, which was determined using X-ray crystallography to a resolution of 1.8 Å.
The microfibrils that are made up of fibrillin protein are responsible for different cell-matrix interactions in the human body.
Fibrillin-2
Fibrillin-2 was isolated in 1994 by Zhang
and is thought to play a role in early
elastogenesis. Mutations in the fibrillin-2 gene have been linked to
Beals syndrome.
Fibrillin-3
More recently, fibrillin-3 was described and is believed to be located mainly in the brain.
Along with the brain, fibrillin-3 has been localized in the gonads and ovaries of field mice.
Fibrillin-4
Fibrillin-4 was first discovered in zebrafish, and has a sequence similar to fibrillin-2.
References
External links
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{{Cytoskeletal proteins
Structural proteins