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Thrombospondin 3 is a pentameric molecule held together by interchain disulfide linkage involving two cysteine
1Department of Pathology, University of Michigan School of Medicine, Ann Arbor 48109, USA.
Insights
Thrombospondin 3 (TSP3) forms a pentameric structure, unlike the trimeric TSP1. This oligomeric assembly is crucial for its function in cell migration and development, mediated by specific cysteine residues.
Area of Science:
- Biochemistry
- Molecular Biology
- Extracellular Matrix Research
Background:
- Thrombospondins (TSPs) are a family of extracellular matrix proteins involved in cell migration and development.
- TSP1, the prototypical member, forms a trimer via NH2-terminal disulfide linkages.
- TSP3 shares sequence similarity with TSP1 but has a distinct NH2 terminus, raising questions about its oligomeric structure.
Purpose of the Study:
- To determine the oligomeric nature of Thrombospondin 3 (TSP3).
- To identify the specific cysteine residues responsible for TSP3 oligomer formation.
Main Methods:
- Deletional and site-directed mutagenesis.
- Rotary shadowing electron microscopy.
Main Results:
- TSP3 forms a pentameric molecule, similar to TSP4 and COMP.
- TSP3 oligomerization is mediated by disulfide linkage between Cys-245 and Cys-248.
Conclusions:
- TSP3 exhibits pentameric assembly, distinct from TSP1's trimeric structure.
- The identified cysteine residues are critical for TSP3's pentameric formation and likely its biological function.
Abstract:
The thrombospondins (TSPs) are a family of 5 distinct gene products designated TSP1, -2, -3, -4, and COMP, for cartilage oligomeric matrix protein. TSP1, the prototypical member, is a trimeric extracellular matrix molecule implicated in cell migration and development. TSP1 trimer formation is mediated by interchain disulfide linkage involving two NH2-terminal cysteines. TSP3, a recent addition to the family, is a developmentally regulated heparin binding protein that is similar in sequence to the COOH terminus of TSP1 but has a distinct NH2 terminus. This has raised the question of the oligomeric nature of TSP3 and identification of the cysteine residues involved in oligomer formation. We demonstrate, using a combination of deletional and site-directed mutagenesis and rotary shadowing electron microscopy, that TSP3, like TSP4 and COMP, is a pentameric molecule. TSP3 is held together by interchain disulfide linkage involving just two cysteine residues, Cys-245 and Cys-248.