Isolation of complexes formed between insulin-like growth factor-binding protein-3 and transferrin from the human serum

Abstract

Insulin-like growth factors (IGFs) play an important role in the regulation of cell growth, differentiation and metabolism. The amount of free, biologically active IGFs is regulated by the IGF-binding proteins (IGFBPs). IGFBP-3 is the most abundant binding protein and it is known to interact with other circulating proteins, including transferrin (Tf). In order to elucidate the possible role of IGF/IGFBP-3 in the iron metabolism, it is necessary to isolate IGFBP-3/Tf complexes. Several affinity-based techniques were employed. Results have shown that only double immunoprecipitation method with anti-Tf and anti-IGFBP-3 antibodies selectively separated complexes from other molecular forms, such as monomers, oligomers or fragments of IGFBP-3 and Tf. Isolated complexes can now be used to investigate the relationship between IGF/IGFBP-3 and iron, both in structural and metabolic t?rms.