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Structure-function analysis of tissue-type plasminogen activator by linker-insertion, point and deletion mutagenesis
W Markland1, D Pollock, D J Livingston
1Protein Engineering Laboratory, Integrated Genetics Inc., Framingham, MA 01701.
Protein Engineering
|November 1, 1989
Summary
Investigating human tissue plasminogen activator (tPA) structure, researchers found that altering any domain, especially conserved residues, significantly impacts its fibrinolytic activity. Mutations in the kringle domains were particularly detrimental.
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Engineering
Background:
- Human tissue plasminogen activator (tPA) is a crucial enzyme in fibrinolysis.
- Understanding the structure-function relationship of tPA is vital for therapeutic development.
Purpose of the Study:
- To perform a structure-function analysis of human tPA.
- To identify key domains and residues critical for tPA activity.
Main Methods:
- Linker-scanning mutagenesis and deletion mutagenesis were employed.
- Synthetic oligonucleotide linkers were introduced into tPA cDNA to create variants.
- Amidolytic and fibrinolytic activity assays were performed on tPA variants.
Main Results:
- Most tPA variants showed reduced amidolytic and fibrinolytic activity compared to wild-type.
- Insertions at the finger domain boundaries (BglII(115) and StyI(277)) were exceptions with retained activity.
- Mutations in the protease domain (light chain) and deletion of kringle domains significantly decreased activity.
- Highly conserved amino acids were particularly sensitive to mutational effects.
Conclusions:
- Alterations in any domain of the tPA molecule can affect fibrinolytic activity.
- Highly conserved residues within tPA domains are critical for maintaining function.
- Kringle domains appear essential for optimal fibrinolytic efficacy.