Protamine interacts with the D-domains of fibrinogen

Abstract

The mechanism of precipitation of fibrinogen in the presence of a basic protein, protamine, has been investigated. The precipitation was clearly inhibited by the addition of Fragment D. Photooxidation of fibrinogen abolished the association caused by thrombin, but it did not affect the precipitation brought about by protamine. Not only fibrinogen but also fibrin monomer precipitated in the presence of protamine. These results led to the conclusion that protamine bound directly with D-domains of fibrinogen (of fibrin monomer) to cause the precipitation.