Description
Unlike insulin, both IGF-I and IGF-II circulate in plasma tightly bound to specific binding proteins. Two major forms of IGF- binding proteins have been identified in human plasma, a low molecular weight form and a high molecular weight form. The low molecular weight IGF-binding protein (IGFBP1) is synthesized in liver, secretory endometrium, and decidua. It binds both IGF I and IGF II with high affinity. Insulin-like growth factor binding protein-1 (IGFBP-1 ~30kD; also known as IBP1 or placental protein 12, or IGF-BP25; chromosome 7p14-p12)) is a member of the superfamily of insulin-like growth factor (IGF) binding proteins which include six high-affinity IGF binding proteins (IGFBP1-6) and at least four low-affinity binding proteins referred to as IGFBP related proteins (IGFBP-rP). The IGFBP members are cysteine-rich proteins with conserved cysteine residues, clustered in the amino-terminal and the carboxy-terminal regions of the molecule. Contained within IGFBP-1 and -2 is an integrin receptor recognition sequence (RGD) that is responsible for promoting cell migration by an IGF- independent action. IGFBPs hold a central position in IGF ligand-receptor interactions through influences on both the bioavailability and distribution of IGFs in the extracellular environment. IGFBPs will either inhibit or enhance the biological activities of IGF or act in an IGF-independent manner.
IGF-BP7 is expressed in a wide range of normal human tissues and it generally shows reduced expression in cancer cell lines of prostate, breast, colon, and lung origin. It plays a role in skeletal myogenesis by binding to IGF in a manner that inhibits IGF induced differentiation of skeletal myoblasts, without affecting IGF induced proliferation. Additionally, IGF-BP7 suppresses growth and colony formation of prostate and breast cancer cell lines through an IGF independent mechanism, which causes a delay in the G1 phase of the cell cycle, and increased apoptosis. Recombinant human IGF-BP7 is a 26.4kD protein consisting of 257aa residues.
Recombinant protein corresponding to aa28-281 of mouse IGFBP7 expressed in Sf21 cells wth human CD33-His tag at the N-terminus. The Human CD33 is removed