Fibulin

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. In vertebrates, fibulin-1 is found in blood and extracellular matrices. In the extracellular matrix, fibulin-1 associates with basement membranes and elastic fibers. The association with these matrix structures is mediated by its ability to interact with numerous extracellular matrix constituents including fibronectin, proteoglycans, 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.

FBLN1

FBLN1 is the gene encoding fibulin-1, an extracellular matrix and plasma protein.

Function

Fibulin-1 is a secreted glycoprotein that is found in association with extracellular matrix structures including fibronectin-containing fibers, elastin-containing fibers and basement membranes. Fibulin-1 binds to a number of extracellular matrix constituents including fibronectin,nidogen-1, and the proteoglycan, versican. Fibulin-1 is also a blood protein capable of binding to fibrinogen.

Structure

Fibulin-1 has modular domain structure and includes a series of nine epidermal growth factor-like modules followed by a fibulin-type module, a module found in all members of the fibulin gene family.

The human fibulin-1 gene, FBLN1, encodes four splice variants designated fibulin-1A, B, C and D, which differ in their carboxy terminal regions. In mouse, chicken and the nematode, C. elegans, only two fibulin-1 variants are produced, fibulin-1C and fibulin-1D.

Interactions

FBLN1 has been shown to interact with: