Diversity of Human Insulin-like Growth Factor (IGF) Binding Protein-2 Fragments in Plasma: Primary Structure, IGF-Binding Properties, and Disulfide Bonding Pattern

详细信息    查看全文

• 作者：Silke Mark ; Bernd Kü ; bler ; Stefan Hö ; ning ; Sandra Oesterreicher ; Harald John ; Thomas Braulke ; Wolf-Georg Forssmann ; and Ludger Stä ; ndker
• 刊名：Biochemistry
• 出版年：2005
• 出版时间：March 8, 2005
• 年：2005
• 卷：44
• 期：9
• 页码：3644 - 3652
• 全文大小：413K
• 年卷期：v.44,no.9(March 8, 2005)
• ISSN：1520-4995

文摘

The insulin-like growth factor binding proteins (IGFBPs) play a major role in the regulationof the effects and the bioavailability of the insulin-like growth factors (IGFs). IGFs are released fromIGFBP-IGF complexes by proteolysis of IGFBPs generating fragments with reduced ligand-bindingproperties. To identify naturally occurring fragments of IGFBP-2, a peptide library generated from humanhemofiltrate was immunologically screened. Purification of immunoreactive IGFBP-2 fragments wasperformed by consecutive chromatographic steps. A total of 18 different IGFBP-2 fragments was isolatedand characterized. The peptides exhibited different N-terminal amino acid residues that were located inthe variable midregion of IGFBP-2. Four major cleavage sites were determined to be between Tyr103and Gly104, Leu152 and Ala153, Arg156 and Glu157, and Gln165 and Met166. The resulting fragmentswere further processed by amino and/or carboxy peptidases and comprised 37-185 amino acid residues.Ligand blotting, solution binding assays, and BIAcore analyses revealed that all tested fragments retainedlow IGF-binding capacity. The most abundant fragment IGFBP-2 (167-279) showed 10% of IGF-II bindingcompared to recombinant human (rh)IGFBP-2. Furthermore, the disulfide bonding pattern of the C-terminaldomain of rhIGFBP-2 was defined, indicating linkages between cysteine residues 191-225, 236-247,and 249-270. This study provides the most comprehensive molecular characterization of human IGFBP-2fragments formed in vivo, exhibiting both residual IGF-binding capacities and the integrin-binding sequence.