Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/11316
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Type: Journal article
Title: The Insulin-like Growth Factor (IGF) Binding Site of Bovine Insulin-like Growth Factor Binding Protein-2 (bIGFBP-2)
Author: Hobba, G.
Forbes, B.
Parkinson, E.
Francis, G.
Wallace, J.
Citation: Journal of Biological Chemistry, 1996; 271(48):30529-30536
Publisher: AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Issue Date: 1996
ISSN: 0021-9258
1083-351X
Abstract: The insulin-like growth factor (IGF) binding site of bovine insulin-like growth factor binding protein 2 (bIGFBP-2) has been probed by chemical iodination. Tyrosyl residues of bIGFBP-2 were reacted by chloramine T-mediated iodination. The modification patterns of free bIGFBP-2 and bIGFBP-2 associated with insulin-like growth factor II (IGF-II) were compared by tryptic mapping using electrospray mass spectrometry and N-terminal sequencing. The presence of bound IGF-II resulted in protection of tyrosine at position 60 from iodination measured by the relative loss of tyrosine specific fluorescence and the incorporation of the radioisotope 125I. In addition, the pattern of iodine incorporation of bIGFBP-2 was not different whether IGF-I or IGF-II was the protective ligand. bIGFBP-2, when iodinated alone sustained a 8-fold loss of binding affinity for IGF-I and a 4-fold loss in binding affinity for IGF-II. In contrast, bIGFBP-2 iodinated while complexed with either IGF-I or IGF-II retained the same binding affinity for IGF-I or IGF-II as non-iodinated bIGFBP-2. We conclude that tyrosine 60 lies either in a region of bIGFBP-2 which directly interacts with both IGF-I and IGF-II or lies in a region of bIGFBP-2 which undergoes a conformational change that is important for IGF binding. Furthermore, iodination of tyrosine residues at positions 71, 98, 213, 226, and 269 has no detectable impact on binding of bIGFBP-2 to the IGFs.
Keywords: Animals; Cattle; Iodine; Trypsin; Tyrosine; Insulin-Like Growth Factor I; Insulin-Like Growth Factor II; Insulin-Like Growth Factor Binding Protein 2; Peptide Mapping; Spectrometry, Fluorescence; Binding Sites; Binding, Competitive; Amino Acid Sequence; Molecular Sequence Data
RMID: 0030004389
DOI: 10.1074/jbc.271.48.30529
Appears in Collections:Biochemistry publications

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