Insulin-like growth factor-binding protein-3 (IGFBP-3) is a member of a family of structurally conserved proteins (IGFBP-1 to -6) which act as carriers and regulators of the mitogenic peptide hormones IGF-I and IGF-II. Members of the IGFBP family share conserved cysteine-rich amino- and carboxyl-terminal regions. The amino-terminal domain of these proteins is recognised to contain an IGF-binding determinant, but evidence to support a binding site in the carboxyl-terminal region of the protein is less rigorous. To further investigate this, we have synthesised both the amino-terminal (residues 1-88; N-88) and carboxyl-terminal (residues 165-264; C-165) domains of human IGFBP-3 in bacteria, as fusion proteins with a carboxyl-terminal FLAG peptide. Although only C-165 showed binding to IGF-I and -II by solution-binding assays, both N-88 and C-165 demonstrated binding to IGF-I and -II by biosensor analysis albeit with reduced affinities compared with full-length IGFBP-3. Only the carboxyl-terminal fragment (C-165) was able to form hetero-trimeric complexes with IGF-I and the acid-labile subunit (ALS). We conclude that the carboxyl-terminal domain of IGFBP-3 contains an IGF-binding determinant and can form ternary complexes with ALS.

This article has been cited by other articles:

				F. R. Santer, B. Moser, G. A. Spoden, P. Jansen-Durr, and W. Zwerschke Human papillomavirus type 16 E7 oncoprotein inhibits apoptosis mediated by nuclear insulin-like growth factor-binding protein-3 by enhancing its ubiquitin/proteasome-dependent degradation Carcinogenesis, December 1, 2007; 28(12): 2511 - 2520. [Abstract] [Full Text] [PDF]

				T. Sitar, G. M. Popowicz, I. Siwanowicz, R. Huber, and T. A. Holak Structural basis for the inhibition of insulin-like growth factors by insulin-like growth factor-binding proteins PNAS, August 29, 2006; 103(35): 13028 - 13033. [Abstract] [Full Text] [PDF]

				M. M. Kibbey, M. J. Jameson, E. M. Eaton, and S. A. Rosenzweig Insulin-Like Growth Factor Binding Protein-2: Contributions of the C-Terminal Domain to Insulin-Like Growth Factor-1 Binding Mol. Pharmacol., March 1, 2006; 69(3): 833 - 845. [Abstract] [Full Text] [PDF]

				G. J. Allan, E. Tonner, M. Szymanowska, J. H. Shand, S. M. Kelly, K. Phillips, R. A. Clegg, I. F. Gow, J. Beattie, and D. J. Flint Cumulative Mutagenesis of the Basic Residues in the 201-218 Region of Insulin-Like Growth Factor (IGF)-Binding Protein-5 Results in Progressive Loss of Both IGF-I Binding and Inhibition of IGF-I Biological Action Endocrinology, January 1, 2006; 147(1): 338 - 349. [Abstract] [Full Text] [PDF]

				J. Beattie, K. Phillips, J. H Shand, M. Szymanowska, D. J Flint, and G. J Allan Molecular recognition characteristics in the insulin-like growth factor (IGF)-insulin-like growth factor binding protein -3/5 (IGFBP-3/5) heparin axis J. Mol. Endocrinol., February 1, 2005; 34(1): 163 - 175. [Abstract] [Full Text] [PDF]

				S. J Headey, K. S Leeding, R. S Norton, and L. A Bach Contributions of the N- and C-terminal domains of IGF binding protein-6 to IGF binding J. Mol. Endocrinol., October 1, 2004; 33(2): 377 - 386. [Abstract] [Full Text] [PDF]

				L. D. Payet, X.-H. Wang, R. C. Baxter, and S. M. Firth Amino- and Carboxyl-Terminal Fragments of Insulin-Like Growth Factor (IGF) Binding Protein-3 Cooperate to Bind IGFs with High Affinity and Inhibit IGF Receptor Interactions Endocrinology, July 1, 2003; 144(7): 2797 - 2806. [Abstract] [Full Text] [PDF]

				J. H. Shand, J. Beattie, H. Song, K. Phillips, S. M. Kelly, D. J. Flint, and G. J. Allan Specific Amino Acid Substitutions Determine the Differential Contribution of the N- and C-terminal Domains of Insulin-like Growth Factor (IGF)-binding Protein-5 in Binding IGF-I J. Biol. Chem., May 9, 2003; 278(20): 17859 - 17866. [Abstract] [Full Text] [PDF]

				S. M. Firth and R. C. Baxter Cellular Actions of the Insulin-Like Growth Factor Binding Proteins Endocr. Rev., December 1, 2002; 23(6): 824 - 854. [Abstract] [Full Text] [PDF]

				P. Vorwerk, B. Hohmann, Y. Oh, R. G. Rosenfeld, and R. M. Shymko Binding Properties of Insulin-Like Growth Factor Binding Protein-3 (IGFBP-3), IGFBP-3 N- and C-Terminal Fragments, and Structurally Related Proteins mac25 and Connective Tissue Growth Factor Measured Using a Biosensor Endocrinology, May 1, 2002; 143(5): 1677 - 1685. [Abstract] [Full Text] [PDF]

				J. Hong, G. Zhang, F. Dong, and M. M. Rechler Insulin-like Growth Factor (IGF)-binding Protein-3 Mutants That Do Not Bind IGF-I or IGF-II Stimulate Apoptosis in Human Prostate Cancer Cells J. Biol. Chem., March 15, 2002; 277(12): 10489 - 10497. [Abstract] [Full Text] [PDF]

				F. E. Carrick, B. E. Forbes, and J. C. Wallace BIAcore Analysis of Bovine Insulin-like Growth Factor (IGF)-binding Protein-2 Identifies Major IGF Binding Site Determinants in Both the Amino- and Carboxyl-terminal Domains J. Biol. Chem., July 13, 2001; 276(29): 27120 - 27128. [Abstract] [Full Text] [PDF]