Description
Thesuperfamily of insulin-like growth factor (IGF) binding proteins include thesix high-affinity IGF binding proteins (IGFBP) and at least four additional low-affinitybinding proteins referred to as IGFBP related proteins (IGFBP-rP). All IGFBPsuperfamily members are cysteine-rich proteins with conserved cysteineresidues, which are clustered in the amino-and carboxy-terminal thirds of themolecule. IGFBPs modulate the biological activities of IGF proteins. SomeIGFBPs may also have intrinsic bioactivity that is independent of their abilityto bind IGF proteins. Post-translational modifications of IGFBPs, includingglycosylation, phosphorylation and proteolysis, have been shown to modify theaffinities of the binding proteins to IGF