title: Isolation and characterization of circulating fragments of the insulin-like growth factor binding protein-3.
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-3(1-98) overexpressing cells bound IGF. Additionally, two smaller fragments (IGFBP-3(139-157) and IGFBP-3(139-159)) 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.
authors: Children's Hospital-Biochemistry, University of Hamburg, Martinistr. 52, D-20246, Hamburg, Germany.
authors: Bernd
authors: B
authors: Kübler
authors: Claudia
authors: C
authors: Draeger
authors: Harald
authors: H
authors: John
authors: Uwe
authors: U
authors: Andag
authors: Jens-Gerd
authors: JG
authors: Scharf
authors: Wolf-Georg
authors: WG
authors: Forssmann
authors: Thomas
authors: T
authors: Braulke
authors: Ludger
authors: L
authors: Ständker
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D006031:Glycosylation; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood* / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000097:blood / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D017434:Protein Structure, Tertiary; D051381:Rats
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D010446:Peptide Fragments