Sequence comparison and predicted structure for the four exon-encoded regions of human insulin-like growth factor binding protein 4

The IGFBPs bind to and modulate the function of the IGFs in various ways. Human IGFBP-4 inhibits IGF mediated cell proliferation. The IGFBP exon-encoded regions were aligned and secondary structure predictions for hIGFBP-4 were developed yielding predicted 3D co-ordinates for each such region of hIGFBP-4. The exon 1 encoded region is the most conserved among the IGFBPs. That of hIGFBP-4 is predicted as an array of βstrands that include the glycine and cysteine rich IGFBP concensus pattern and that terminate with a helix. The exon 2 encoded region is the most variable among the IGFBPs. That of hIGFBP-4 is predicted as mostly an amphipathic helix. The remaining regions are also conserved among the IGFBPs. Those of hIGFBP-4 are also predicted to contain helices. The predicted structure of hIGFBP-4 comprises amino terminal βstrands with four helices in the carboxy terminal two thirds of the molecule.