ABSTRACT
The sequence of urokinase-type plasminogen activator (uPA) is highly homologous to a variety of other fibrinolytic and coagulation factors, and in a small region of the growth factor domain to some growth factors like epidermal growth factor, TGF-alpha. The data are thus in keeping with the idea that receptor-bound uPA is involved in cell migration and invasion. The ability of aminoterminal fragment to bind to U937 cells receptors locates the region responsible for receptor binding in the amino terminal moiety of uPA, within residues 1-135. Binding to receptor and enzymatic activity, therefore, are indeed independent functions located in different domains of the molecule. When the uPA receptor was discovered, it was soon realized that the interaction between uPA and its receptor was species-specific. Plasminogen receptors have been observed in a variety of cells. Their affinity is in general not as high as that of uPA receptors, but the number is larger.
