Deglycosylated prothrombin fragment 1. Calcium binding, phospholipid interaction, and self-assocation

Area of Science:

• Biochemistry
• Protein Chemistry
• Molecular Biology

Background:

• Prothrombin fragment 1 plays a crucial role in blood coagulation.
• Its calcium- and membrane-binding properties are essential for function.
• The role of its carbohydrate moiety in these interactions is not fully understood.

Purpose of the Study:

• To investigate the impact of carbohydrate removal on prothrombin fragment 1's functional properties.
• To elucidate the role of carbohydrates in protein self-association and conformational changes.

Main Methods:

• Fluorolysis using anhydrous HF to remove carbohydrate groups.
• Monitoring calcium- and membrane-binding properties.
• Assessing protein self-association using fluorescence spectroscopy.
• Investigating protein-membrane interactions and EDTA-induced reversal.

Main Results:

• Deglycosylation did not affect calcium- and membrane-binding capabilities.
• Both native and deglycosylated proteins exhibited rapid, calcium-dependent dimerization.
• Deglycosylated protein showed a secondary, slower self-association linked to conformational changes.
• This secondary association occurred on membrane surfaces, suggesting exposed binding sites.

Conclusions:

• The carbohydrate portion of prothrombin fragment 1 is not essential for calcium or membrane binding.
• Carbohydrates appear to mask a site involved in secondary protein self-association.
• Calcium-dependent conformational changes expose this site, facilitating further protein interactions.