Three-dimensional modeling of thrombin-fibrinogen interaction

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Modeling

Background:

• Thrombin is a key enzyme in blood coagulation.
• Fibrinogen is a primary substrate of thrombin, crucial for clot formation.
• Understanding thrombin-fibrinogen interaction is vital for hemostasis research.

Purpose of the Study:

• To present three-dimensional models of thrombin complexed with fibrinogen fragments.
• To elucidate the molecular basis of thrombin-fibrinogen recognition.
• To identify key structural motifs involved in substrate binding.

Main Methods:

• Construction of three-dimensional models based on existing thrombin and fibrinogen data.
• Analysis of mutagenesis and natural mutant data for consistency.
• Identification of conserved motifs and binding surfaces.

Main Results:

• Detailed models of thrombin complexed with fibrinogen Aalpha and Bbeta chain fragments.
• Identification of Tyr(76) in exosite I and the aryl binding site as critical for recognition.
• Discovery of a conserved aromatic-Pro-aromatic triplet motif in fibrinogen and other substrates.
• The triplet motif orients substrates for optimal binding to exosite I and the active site.

Conclusions:

• Thrombin utilizes an extended binding surface for fibrinogen recognition.
• The aromatic-Pro-aromatic triplet motif plays a crucial role in substrate orientation.
• These findings suggest a generalizable pattern for thrombin's recognition of natural substrates.