Evidence that type 1 plasminogen activator inhibitor binds to the somatomedin B domain of vitronectin.
The interaction between type 1 plasminogen activator inhibitor (PAI-1) and fragments of vitronectin (Vn) was investigated. The PAI-1-binding domain was not destroyed when Vn was cleaved by treatment with either acid or CNBr. Acid-cleaved Vn was fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and analyzed by PAI-1 ligand binding. The smallest fragment (Mr 40,000) that retained PAI-1 binding function was sequenced and shown to contain the NH2 terminus of the molecule. Further cleavage of this fragment by treatment with CNBr generated a Mr 35,000 fragment (Pro52-Asp239) that did not interact with PAI-1, and a Mr 6,000 NH2-terminal fragment (Asp1-Met51) that spanned the somatomedin B domain and contained the RGD (cell binding) sequence. The purified Mr 6,000 fragment competed with immobilized Vn for PAI-1 binding, and formed complexes with activated PAI-1. These complexes could be immunoprecipitated by antibodies to PAI-1. Synthetic peptides containing the RGD sequence had no effect on the binding of this fragment to PAI-1. These results suggest that the cell-binding and PAI-1 binding sequences of Vn occupy distinct regions in the NH2-terminal somatomedin B domain of the molecule.
Seiffert
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Committee on Vascular Biology, Research Institute of Scripps Clinic, La Jolla, California 92037.
Loskutoff
D J
DJ
D000596:Amino Acids / Q000032:analysis; D002850:Chromatography, Gel; D003488:Cyanogen Bromide; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism; D006801:Humans; D015849:Plasminogen Inactivators / Q000378:metabolism*; D013002:Somatomedins / Q000378:metabolism*; D019096:Vitronectin
D000596:Amino Acids; D006023:Glycoproteins; D015849:Plasminogen Inactivators; D013002:Somatomedins; D019096:Vitronectin; C016756:somatomedin B; D006493:Heparin; D003488:Cyanogen Bromide