Phospholipid-specific conformational changes in human prothrombin upon binding to procoagulant acidic lipid membranes

Area of Science:

• Biochemistry
• Molecular Biology
• Protein Structure

Background:

• Prothrombin activation is a critical step in blood coagulation.
• Procoagulant membranes, particularly those containing phosphatidylserine (PS), are known to accelerate this process.
• The precise molecular mechanisms underlying this acceleration are not fully understood.

Purpose of the Study:

• To investigate the conformational changes in human prothrombin upon binding to procoagulant membranes.
• To elucidate the role of phosphatidylserine (PS) in mediating these structural alterations.
• To compare these changes with those induced by other negatively-charged lipids.

Main Methods:

• Fourier transform infrared (FTIR) spectroscopy to analyze secondary structure.
• Differential scanning calorimetry (DSC) to study protein denaturation and domain organization.
• Utilized human prothrombin and prothrombin fragment 1.

Main Results:

• Human prothrombin exhibited a slight increase in ordered secondary structures (alpha-helix, beta-sheet, beta-turns) upon binding to PS-containing membranes.
• Differential scanning calorimetry revealed changes in the domain organization of prothrombin when bound to PS.
• Minimal structural changes were observed when prothrombin interacted with phosphatidylglycerol-containing membranes.

Conclusions:

• Binding to PS-containing membranes induces significant conformational changes in human prothrombin.
• These structural alterations are likely key to the cofactor-like role of platelet membrane vesicles in prothrombin activation.
• The findings support a molecular mechanism for enhanced prothrombin activation on specific membrane surfaces.