Fibronectin self-association is mediated by complementary sites within the amino-terminal one-third of the molecule.
The formation of a fibrillar fibronectin (FN) extracellular matrix requires self-association of FN dimers. In this report, we show that the major sites for self-association are the amino-terminal repeats I1-5 and the first type III repeats. Recombinant FNs and fragments were generated by baculovirus expression of cysteine-rich domains and by bacterial expression of type III repeats as fusion proteins with maltose binding protein. When recombinant polypeptides were immobilized on microtiter wells, FN bound to 70-kDa amino-terminal fragment and to fusion proteins containing repeats III1-2 and III1-6 but not to other type III repeats. Similar results were obtained with a gel overlay assay. Binding was concentration-dependent and saturable. The amino-terminal binding site for III1-2 was further localized to repeats I1-5. Therefore, at least two different sites for FN-FN interaction reside near the amino terminus of the molecule. A model for the regulation of FN matrix assembly is proposed based on intramolecular interactions between these amino-terminal sites.
Department of Molecular Biology, Princeton University, New Jersey 08544-1014.
K M
KM
Aguirre
R J
RJ
McCormick
J E
JE
Schwarzbauer
D000595:Amino Acid Sequence; D000818:Animals; D016367:Baculoviridae; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005353:Fibronectins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008320:Maltose / Q000378:metabolism; D058619:Maltose-Binding Proteins; D008961:Models, Structural; D008970:Molecular Weight; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D018411:Spodoptera; D014162:Transfection
D002352:Carrier Proteins; D005353:Fibronectins; D058619:Maltose-Binding Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D008320:Maltose