Research conducted in the Morrissey laboratory focuses on understanding how cells regulate blood clotting in health and disease. The blood clotting system is activated when an enzyme (a specific plasma serine protease known as factor VIIa) binds to a particular integral membrane protein (known as tissue factor, or TF) on cell surfaces. The TF-VIIa-membrane complex triggers the blood clotting cascade by activating two plasma serine protease zymogens (factor IX and factor X) via limited proteolysis.