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Isolation and characterization of circulating fragments of the insulin-like growth factor binding protein-3

By Bernd Kübler, Claudia Draeger, Harald John, Uwe Andag, Jens-Gerd Scharf, Wolf-Georg Forssmann, Thomas Braulke and Ludger Ständker

Abstract

AbstractProteolysis 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

Publisher: Published by Elsevier B.V.
Year: 2002
DOI identifier: 10.1016/S0014-5793(02)02673-X
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