Dissociation of thrombin's substrate interactions using site-directed mutagenesis

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Thrombin is a key allosteric enzyme in blood coagulation, interacting with various procoagulant and anticoagulant substrates.
• Understanding thrombin's substrate interactions is crucial for developing targeted therapies.

Purpose of the Study:

• To functionally map thrombin's interactions with its substrates using mutagenesis.
• To identify specific thrombin mutants with altered procoagulant and anticoagulant activities.

Main Methods:

• Systematic alanine scanning mutagenesis was employed to generate a library of thrombin mutants.
• Characterization of mutant thrombin activity towards specific clotting factors, protein C, and thrombomodulin.

Main Results:

• A specific mutant, E229K, was identified with significantly reduced procoagulant properties.
• The E229K mutant retained its ability to activate protein C, exhibiting anticoagulant function in vitro and in vivo.
• Distinct domains of thrombin were implicated in interactions with thrombomodulin (TM) and subsequent activation of protein C and thrombin-activatable fibrinolysis inhibitor (TAFI).

Conclusions:

• The E229K thrombin mutant serves as a valuable tool for studying anticoagulation mechanisms.
• Specific domains within thrombin play critical roles in substrate recognition and enzyme function, particularly in the context of thrombomodulin interactions.