Igf binding proteins

Abstract

IGFBP-3 fusion proteins are provided that are useful, for example, in cell-based assays, as IGF antagonists, and in mapping IGF-I and IGF-II binding sites on other molecules such as wild-type IGFBP-3 and IGF agonist peptides identified by phage display. Methods for making such fusion proteins are also provided.

1 . A method for determining a biological activity of an agonist of a native-sequence human insulin-like growth factor-I (IGF-I) in a cell-based assay comprising contacting cells with a fusion protein comprising a peptide linked to an IGFBP-3 fragment that binds to IGF-I, rather than with native-sequence human insulin-like growth factor binding protein-3 (IGFPB-3), and determining if a biological activity attributable to an agonist of said native-sequence human IGF-I is observed. 
     
     
         2 . The method of  claim 1  wherein the peptide of the fusion protein is SEQ ID NO:10. 
     
     
         3 . The method of  claim 1  wherein the IGFBP-3 fragment is a fragment of residues 47 to 99 of native-sequence human IGFBP-3 (SEQ ID NO:1). 
     
     
         4 . The method of  claim 1  wherein the biological activity is apoptosis of native-sequence human IGFBP-3 that is independent of IGF-I. 
     
     
         5 . The method of  claim 1  wherein the method is an IGF-dependent KIRA phosphorylation method. 
     
     
         6 . The method of  claim 1  wherein the biological activity is inhibition of binding of radiolabeled IGF-I to the cells.