Identification of a novel integrin binding site in fibronectin. Differential utilization by beta 3 integrins.
Fibronectin (Fn) binding to the integrins alpha IIb beta 3 and alpha v beta 3 involves the Arg-Gly-Asp sequence. The identification of other regions of Fn that interact with alpha IIb beta 3 suggests a potential mechanism for differential ligand recognition by integrins. We report here the identification of an 11-residue peptide sequence from the 9th type III repeat of Fn (3Fn9), which inhibits ligand binding to alpha IIb beta 3 by interacting directly with this receptor. Mutational analysis demonstrated that this same region was involved in the formation of epitopes for two anti-Fn mAbs that inhibit Fn binding to alpha IIb beta 3, thus emphasizing the role of this site in the macromolecule. Molecular modeling of the 3Fn9-10 modules suggested that Fn residues Asp1373-Thr1383 are at least 25 A distant from the Arg-Gly-Asp site and therefore does not directly interact with it. The 3Fn9 site was differentially recognized by the beta 3 integrin family. The Asp1373-Thr1383 peptide failed to inhibit ligand binding to alpha v beta 3, a recombinant Fn Ala1235-Ser1436 fragment was not recognized by alpha v beta 3, and addition of the 3Fn9 module to the amino terminus of the 3Fn10 did not affect the potency of inhibition of Fn binding to alpha v beta 3. Thus, a novel integrin recognition site in the 3Fn9 module of Fn that is differentially recognized by the beta 3 integrins has been localized within the residues Asp1373-Thr1383.
Bowditch
R D
RD
Department of Vascular Biology, Scripps Research Institute, La Jolla, California 92037.
Hariharan
M
M
Tominna
E F
EF
Smith
J W
JW
Yamada
K M
KM
Getzoff
E D
ED
Ginsberg
M H
MH
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000276:immunology; D001483:Base Sequence; D001665:Binding Sites; D017931:DNA Primers; D000939:Epitopes / Q000276:immunology; D005353:Fibronectins / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010974:Platelet Aggregation
D000596:Amino Acids; D000911:Antibodies, Monoclonal; D017931:DNA Primers; D000939:Epitopes; D005353:Fibronectins; D016023:Integrins; D008024:Ligands