Protamine sulfate interacts with heparin, binding with it to form an acid-base complex. The complex is then removed from circulation.
Heparin binds to antithrombin III, and thrombin and Factor Xa are the most sensitive to its actions. The complex formed by ATIII and heparin also inactivates factors IX, XI, and XII. (Warfarin blocks production of Factors VII, IX, X, and II by the liver.)
Unfortunately that's all I know. I'don't know the answer to your other question; I only know the pharm because I did my preceptorship on a cardiac floor, and I looked it up one night when we were all wondering about it! When I look up stuff on my own I tend to remember it better.
Straight from my Pharmacology book.
Protamine sulfate is an antidote to severe heparin overdose. Protamine is a small protein that has multiple positively charged groups. These charged groups bond ionically with the negative groups on heparin, thereby forming a heparin-protamine complex that is devoid of anticoagulant activity.