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Self-assembly and calcium-binding sites in laminin. A three-arm interaction model
1Department of Pathology, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854.
The Journal of Biological Chemistry
|August 15, 1993
Summary
Laminin polymerization into basement membrane-like networks is calcium-dependent. Assembly requires interactions between short arm fragments, with calcium binding to the B2 short arm activating polymerization.
Area of Science:
- Biochemistry
- Cell Biology
- Extracellular Matrix Research
Background:
- Laminin is a crucial glycoprotein forming networks in basement membranes.
- Understanding laminin assembly is key to comprehending tissue structure and function.
Purpose of the Study:
- To dissect the calcium-dependent assembly of laminin into networks.
- To identify the specific fragments and interactions involved in laminin polymerization.
Main Methods:
- Proteolytic fragment analysis
- Equilibrium gel filtration
- Ultracentrifugation
- Electron microscopy
- Calcium binding assays
Main Results:
- The cathepsin G fragment C1-4 (three short arms) aggregated similarly to laminin.
- Assembly was inhibited by elastase short arm fragments E4 and E1'.
- Fragment E4 bound E1' in a calcium-dependent manner, forming dimers and oligomers.
- Calcium ions bound to fragment E1' at the B2 chain end.
Conclusions:
- Laminin polymerization requires interactions among all three short arm ligands.
- Calcium binding to the B2 short arm fragment (E1') activates network assembly.
- This study elucidates the molecular mechanism of laminin polymerization.