Fibulin (FY-beau-lin) (now known as Fibulin-1
FBLN1) is the prototypic member of a multigene family, currently with seven members. Fibulin-1 is a
calcium-binding glycoprotein Calcium-binding proteins are proteins that participate in calcium signaling, calcium cell signalling pathways by binding to Ca2+, the calcium ion that plays an important role in many cellular processes. Calcium-binding proteins have specific domains ...
. In
vertebrates,
fibulin-1 is found in
blood and
extracellular matrices. In the extracellular matrix, fibulin-1 associates with
basement membrane
The basement membrane is a thin, pliable sheet-like type of extracellular matrix that provides cell and tissue support and acts as a platform for complex signalling. The basement membrane sits between Epithelium, epithelial tissues including mesot ...
s and
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 air ...
s. The association with these matrix structures is mediated by its ability to interact with numerous extracellular matrix constituents including
fibronectin,
proteoglycan
Proteoglycans are proteins that are heavily glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalently attached glycosaminoglycan (GAG) chain(s). The point of attachment is a serine (Ser) residue to whic ...
s,
laminins and
tropoelastin. In blood, fibulin-1 binds to
fibrinogen and incorporates into clots.
Fibulins are secreted glycoproteins that become incorporated into a fibrillar extracellular matrix when expressed by cultured cells or added exogenously to cell monolayers.
The five known members of the family share an elongated structure and many calcium-binding sites, owing to the presence of tandem arrays of epidermal growth factor-like domains. They have overlapping binding sites for several basement-membrane proteins, tropoelastin, fibrillin, fibronectin and proteoglycans, and they participate in diverse supramolecular structures. The amino-terminal domain I of fibulin consists of three
anaphylatoxin-like (AT) modules, each approximately 40 residues long and containing four or six cysteines. The structure of an AT module was determined for the complement-derived anaphylatoxin C3a, and was found to be a compact alpha-helical fold that is stabilized by three disulphide bridges in the pattern Cys14, Cys25 and Cys36 (where Cys is cysteine). The bulk of the remaining portion of the fibulin molecule is a series of nine EGF-like repeats.
Genes
*
FBLN1,
FBLN2,
FBLN3,
FBLN4,
FBLN5,
FBLN7 and
HMCN1 is also known as "fibulin-6".
References
External links
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Protein domains
Blood proteins
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