The inclusion of the type III repeat ED-B in the fibronectin molecule generates conformational modifications that unmask a cryptic sequence.
We have previously reported an anti-fibronectin monoclonal antibody (mAb) (BC-1) which reacts with an ED-B-containing beta-galactosidase-fibronectin fusion protein but not with an identical beta-galactosidase-fibronectin fusion protein in which the ED-B sequence is omitted. In further experiments aimed at localizing more precisely the epitope recognized by this mAb, we demonstrate that 1) the mAb BC-1 is indeed specific for ED-B-containing fibronectin (FN) molecules even though the epitope recognized by this mAb is localized on the type III homology repeat 7 (the one which precedes the ED-B sequence) and 2) in fibronectin molecules lacking the ED-B sequence, this epitope is masked. We further demonstrate that, to mask the epitope recognized by the mAb BC-1, the presence of at least half of the FN type III homology repeat 9 is necessary. We also report the production of the mAb IST-6 which recognizes only FN molecules in which the ED-B sequence is lacking. These data clearly demonstrate that the presence of the ED-B sequence within FN molecules generates conformational modification in the central part of the molecules that unmasks previously cryptic sequences and masks others.
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D002460:Cell Line; D002461:Cell Line, Transformed; D003001:Cloning, Molecular; D000939:Epitopes / Q000032:analysis; D004926:Escherichia coli / Q000235:genetics; D005353:Fibronectins / Q000737:chemistry* / Q000235:genetics* / Q000276:immunology; D006801:Humans; D007124:Immunoenzyme Techniques; D046911:Macromolecular Substances; D011487:Protein Conformation; D011863:Radioimmunoassay; D011993:Recombinant Fusion Proteins / Q000276:immunology; D012091:Repetitive Sequences, Nucleic Acid; D017386:Sequence Homology, Amino Acid; D001616:beta-Galactosidase / Q000235:genetics / Q000276:immunology
D000911:Antibodies, Monoclonal; D000939:Epitopes; D005353:Fibronectins; D046911:Macromolecular Substances; D011993:Recombinant Fusion Proteins; D001616:beta-Galactosidase