Changes in Internal Structure and Dynamics upon Binding Stabilise the Nematode Anticoagulant NAPc2

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Abnormal blood coagulation presents significant health challenges, driving research into novel anticoagulant therapeutics.
• Natural anticoagulants derived from blood-feeding organisms are promising candidates for therapeutic development.
• NAPc2, a nematode-derived coagulation factor Xa modulator, exhibits a unique mechanism of action.

Purpose of the Study:

• To elucidate the molecular mechanism of NAPc2's interaction with coagulation factor Xa.
• To investigate the structural basis for NAPc2's function and stability.
• To explore the potential of conserved stabilizing mechanisms in protease inhibitors.

Main Methods:

• Molecular dynamics simulations were employed to model the interaction between NAPc2 and coagulation factor Xa.
• Mutagenesis studies and clotting time assays were performed to validate simulation findings.
• Analysis focused on conformational changes and stabilizing interactions within the NAPc2-factor Xa complex.

Main Results:

• Simulations indicated that NAPc2 undergoes conformational stabilization upon binding factor Xa.
• A conserved internal salt bridge formed by two key residues was identified as crucial for stabilizing the bound conformation.
• Mutant analysis confirmed the importance of this salt bridge in maintaining NAPc2's functional conformation.

Conclusions:

• The internal salt bridge is essential for stabilizing the bound conformation of NAPc2.
• This salt bridge represents a conserved mechanism for stabilizing secondary structure-poor protease inhibitors.
• Understanding these interactions could inform the design of novel anticoagulant therapies.