Figure 1.

Structure of the human mature IGFBP5 protein. Three major domains, the N-terminal (N), the linker (L) and the C-terminal (C) domain, can be distinguished, which fulfill different functions as indicated. For high affinity IGF binding, the C-terminal domain is required in addition to the primary IGF binding site (IB) within the N-terminal domain between aa 68 and 74. A nuclear localization signal (NLS) is located within the C-terminal domain between aa 201 and 218, which also mediates binding of the IGFBP5 protein to heparin.