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Bone acidic glycoprotein-75 self-associates to form large macromolecular complexes
J P Gorski1, E A Kremer, Y Chen
1Division of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City 64110, USA. JPGORSKI@CCTR.UMKC.EDU
Connective Tissue Research
|January 1, 1996
Summary
Bone acidic glycoprotein-75 (BAG-75) self-associates into large complexes in bone matrix. These BAG-75 complexes may provide mechanical support and aid in bone mineralization.
Area of Science:
- Biochemistry
- Biomaterials Science
- Skeletal Biology
Background:
- Bone acidic glycoprotein-75 (BAG-75) is an acidic phosphoprotein found in bone.
- Osteopontin and bone sialoprotein are other acidic phosphoproteins in bone matrix.
- The in vivo behavior and function of BAG-75 complexes are not well understood.
Purpose of the Study:
- To investigate the self-association properties of BAG-75 in vitro and in vivo.
- To determine the potential role of BAG-75 complexes in bone structure and mineralization.
- To estimate the quantity of BAG-75 in rat calvarial bone.
Main Methods:
- In vitro studies of BAG-75 self-association at varying concentrations.
- Analysis of crude bone and calcified cartilage extracts for BAG-75 complexes.
- Estimation of BAG-75 quantity in rat calvarial bone.
Main Results:
- BAG-75 self-associates to form large fibrillar complexes above 7 x 10(-8) M.
- Similar sized BAG-75 complexes were found in bone and calcified cartilage extracts.
- The amount of BAG-75 in rat calvarial bone is equivalent to osteopontin.
- Calcium binding is not required for BAG-75 self-association.
Conclusions:
- BAG-75 forms macromolecular complexes in vivo, contributing to the mineralized matrix.
- These BAG-75 complexes may function in mechanical support and as an ionic barrier.
- BAG-75 complexes could concentrate phosphate ions, facilitating bone mineralization.