Purification and characterization of bovine tissue factor

Area of Science:

• Biochemistry
• Molecular Biology
• Hematology

Background:

• Tissue factor (TF), also known as tissue thromboplastin or factor III, is a key initiator of the coagulation cascade.
• Understanding TF's structure and function is crucial for studying hemostasis and thrombosis.
• Previous purification methods were often inefficient for this integral membrane glycoprotein.

Purpose of the Study:

• To achieve a high-fold purification of active tissue factor from bovine brain.
• To develop a robust and scalable method for isolating membrane proteins.
• To confirm the identity and activity of the purified protein.

Main Methods:

• Extraction of bovine brain tissue using Triton X-100.
• Purification via repeated preparative SDS-polyacrylamide gel electrophoresis.
• Generation of antiserum for affinity purification using an immunoadsorbent column.
• Tryptic digestion to identify the active component and assess its molecular weight.

Main Results:

• Achieved a 142,000-fold purification of homogeneous tissue factor.
• Identified the apoprotein as an integral membrane glycoprotein with a molecular weight of 43,000 Da.
• Demonstrated that tryptic digestion of a small peptide (3,000 Da) did not abolish coagulant activity.
• Reconstituted coagulant activity with phospholipids, with optimal activity at high phospholipid-to-protein ratios (>450:1).

Conclusions:

• A highly efficient and scalable purification strategy for membrane proteins, including tissue factor, was established.
• The purified protein exhibiting coagulant activity was confirmed to be tissue factor.
• The findings provide a foundation for further structural and functional studies of tissue factor.