Functional consequences of tryptophan modification in human fibrinogen

Area of Science:

• Biochemistry
• Protein Chemistry
• Molecular Biology

Background:

• Fibrinogen is a key protein in blood coagulation.
• Understanding fibrinogen's structure-function relationship is crucial for hemostasis research.
• Oxidative modifications can impact protein function.

Purpose of the Study:

• To investigate the effects of oxidative modification on human fibrinogen.
• To determine the role of specific tryptophan residues in fibrinogen polymerization.

Main Methods:

• Human fibrinogen was modified using hydrogen peroxide (H2O2).
• Oxidative damage to amino acid residues (tryptophan, methionine, tyrosine) was assessed.
• Fibrinogen polymerization activity with thrombin was measured.
• Site-directed modification of tryptophan residues using 2-hydroxy-5-nitrobenzyl bromide was performed.

Main Results:

• H2O2 modification induced inter- and intra-molecular cross-links and oxidized amino acid residues.
• These cross-links were associated with tryptophan oxidation.
• H2O2 modification significantly decreased fibrinogen polymerization activity.
• Modifying two specific tryptophan residues in Fragment D enhanced polymerization activity 1.7-fold.
• Further modification of two additional tryptophan residues in Fragment E abolished polymerization activity.

Conclusions:

• Oxidative cross-linking of fibrinogen impacts its polymerization.
• Specific tryptophan residues in Fragment D and E are critical for thrombin-induced fibrinogen polymerization.
• Targeted modification of these tryptophan residues can modulate fibrinogen function.