1. Isolation and characterization of circulating fragments of the insulin-like growth factor binding protein-3
- Author
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Kübler, Bernd, Draeger, Claudia, John, Harald, Andag, Uwe, Scharf, Jens-Gerd, Forssmann, Wolf-Georg, Braulke, Thomas, and Ständker, Ludger
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INSULIN-like growth factor-binding proteins , *PROTEOLYSIS - Abstract
Proteolysis of insulin-like growth factor binding protein-3 (IGFBP-3), the major carrier of IGFs in the circulation, is an essential mechanism to regulate IGF bioavailability. To analyze naturally occurring IGFBP-3 fragments a peptide library established from human hemofiltrate was screened. Three IGFBP-3 fragments were detected with apparent molecular masses of 34, 16, and 11 kDa. Mass spectrometric and sequence analysis identified the 16 and 11 kDa peptides as glycosylated and non-glycosylated N-terminal fragments spanning residues Gly1–Ala98 of IGFBP-3. Both the circulating forms and those secreted from IGFBP-31–98 overexpressing cells bound IGF. Additionally, two smaller fragments (IGFBP-3139–157 and IGFBP-3139–159) were identified in the hemofiltrate. The data indicate that proteolysis of circulating IGFBP-3 occurs in the variable domain at residues alanine 98, phenylalanine 138, glutamine 157, and tyrosine 159. [Copyright &y& Elsevier]
- Published
- 2002
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