title: Binding of mouse and human fibulin-2 to extracellular matrix ligands.
abstract: Recombinant mouse and human fibulin-2 were obtained as disulfide-bonded trimers from transfected kidney cell clones and used in solid phase, biosensor and radioligand binding assays. Strong binding occurred with fibronectin and required calcium. A distinct interaction was also observed with nidogen but this was only partially blocked by EDTA. Distinctly weaker affinities were detected for collagen IV, perlecan and the N-terminal globule of collagen VI alpha 3 chain, while no or only little binding activity could be detected for several other collagen types, laminin-1, BM-40, fibulin-1 and vitronectin. This weaker binding reactions were also dependent on calcium. Surface plasmon resonance assays demonstrated for fibulin-2 binding to nidogen and fibronectin high equilibrium dissociation constants (0.5 to 1 microM) due to a rapid initial dissociation of the complexes. This is apparently followed by a slower stabilizing reaction. The fibulin-2 binding site of nidogen could be localized to its C-terminal globular domain G3, which also possesses a high-affinity binding site for laminin-1. Several tests demonstrated competition between the two ligands, probably due to steric hindrance. Binding of nidogen to immobilized fibulin-2 allowed the formation of ternary complexes with collagen IV, perlecan and fibulin-1, which, as shown previously, bind independently of the G3 domain. This indicated multifunctional binding properties for fibulin-2 and several alternative routes for its integration into basement membranes and other extracellular structures.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002999:Clone Cells; D005109:Extracellular Matrix / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D016326:Extracellular Matrix Proteins; D008024:Ligands; D011994:Recombinant Proteins; C084612:fibulin 2