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Structure-function analysis of the human insulin-like growth factor binding protein-4
X Qin1, D D Strong, D J Baylink
1Department of Mineral Metabolism, J. L. Pettis Memorial Veterans Medical Center, Loma Linda, California 92357, USA.
The Journal of Biological Chemistry
|August 29, 1998
Summary
Insulin-like growth factor binding protein-4 (IGFBP-4) inhibits insulin-like growth factor (IGF) actions by binding to specific domains. The N-terminal (Leu72-Ser91) and C-terminal (Cys205-Val214) sequences are crucial for high-affinity IGF binding and IGFBP-4 function.
Area of Science:
- Molecular biology
- Endocrinology
- Bone biology
Background:
- Insulin-like growth factor binding protein-4 (IGFBP-4) modulates insulin-like growth factor (IGF) actions.
- Understanding the molecular mechanisms of IGFBP-4 is crucial for its role in human osteoblasts.
Purpose of the Study:
- To identify the molecular mechanism of IGFBP-4's inhibitory effects on IGF actions.
- To localize and determine the role of the IGF binding domain in modulating IGF actions in human osteoblasts.
Main Methods:
- Deletion analysis of IGFBP-4 expressed in bacteria.
- Mitogenic studies using IGFBP-4 mutants and peptides.
- Assessment of IGF binding activity and inhibition of IGF-II-induced osteoblast proliferation.
Main Results:
- The N-terminal sequence Leu72-Ser91 is essential for IGF binding.
- The C-terminal residues Cys205-Val214 facilitate IGF binding.
- IGFBP-4's inhibitory function on osteoblast proliferation is dependent on its IGF binding domain.
Conclusions:
- The N-terminal (Leu72-Ser91) and C-terminal (Cys205-Val214) sequences are necessary for high-affinity IGF binding.
- The IGF binding domain is the major structural determinant of IGFBP-4 function in human osteoblasts.