Isolation and characterization of circulating fragments of the insulin-like growth factor binding protein-3.
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.
Kübler
Bernd
B
Children's Hospital-Biochemistry, University of Hamburg, Martinistr. 52, D-20246, Hamburg, Germany.
Draeger
Claudia
C
John
Harald
H
Andag
Uwe
U
Scharf
Jens-Gerd
JG
Forssmann
Wolf-Georg
WG
Braulke
Thomas
T
Ständker
Ludger
L
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
D018972:Insulin-Like Growth Factor Binding Protein 3; D010446:Peptide Fragments