Molecular interaction site on procoagulant myosin for factor Xa-dependent prothrombin activation

Area of Science:

• Biochemistry
• Molecular Biology
• Hematology

Background:

• Skeletal muscle myosin exhibits procoagulant activity by enhancing thrombin generation.
• Myosin binds coagulation factors Xa and Va, accelerating prothrombin activation.
• A known myosin inhibitor targets the neck region, suggesting this area's importance.

Purpose of the Study:

• To identify the specific binding site(s) on skeletal muscle myosin for coagulation factor Xa.
• To investigate the role of myosin's neck region in its procoagulant activity.

Main Methods:

• Screening of 19 peptides from myosin's neck region for inhibition of myosin-supported prothrombin activation.
• Testing peptide inhibition specificity against phospholipid vesicle-enhanced prothrombin activation.
• Factor Xa binding studies using immobilized peptides.

Main Results:

• Peptide HC796-835 strongly inhibited myosin-enhanced prothrombin activation but not phospholipid-enhanced activation.
• Peptide HC816-837 (C-terminal half of HC796-835) also inhibited myosin-dependent prothrombin activation specifically.
• Factor Xa directly bound to immobilized peptides HC796-835 and HC816-837.

Conclusions:

• Myosin heavy chain (HC) residues 816-835 in the neck region directly bind factor Xa.
• These residues, along with light chain contributions, form myosin's procoagulant surface.
• Identified binding site offers potential for therapeutic targeting of myosin's procoagulant activity.